If you consider yourself a fairly advanced Linux user, I would (as one who has used nearly every Linux distribution worth talking about) highly recommend Sabayon Linux. At least from my own experience using it, Sabayon is the best Linux distribution overall. Here are some of the reasons why:

Rolling release; updated weekly:
Sabayon's repositories are updated weekly with the latest and greatest packages available. Because all Sabayon packages are built off of Gentoo, all packages available in Gentoo are also available in Sabayon (only in the binary (pre-compiled) format. As a result you get the cutting-edge stability of Gentoo, but without the time-waste or compiler headache.

In addition, Sabayon packages are about as close to vanilla (a term used to refer to the original experience provided by the package maintainers) as it gets, so expect a more pure experience. This means that Sabayon GNOME 3 is pure GNOME 3, Sabayon KDE is pure KDE, and Sabayon LXDE is...well you get the point. Most Sabayon distributions include the customization of the appearance of the user interface, but to ensure that the pure vanilla experience is provided, these customizations are done without modification of the packages the UI builds upon.

Highly stable
I have never had a major crash in my use of Sabayon, and as a heavy poweruser who gets off to pushing his operating system to the max, I think my words carry some weight in this regard. In no small measure due to its use of Gentoo Linux as a base, Sabayon is a very stable and reliable operating system.

Cutting edge
If there is a distribution more cutting-edge than Sabayon, let me know. I have never seen any Linux distribution come close to having as recent of packages-- not even Gentoo itself. Even Ubuntu with their army of almighty PPAs can best Sabayon in this category only with more popular packages; in the end, if you want the absolute latest and greatest open-source software, Sabayon is your best bet.

[Note: Gentoo can be as cutting-edge as Sabayon, but not by default. You must configure the ~x86/~x86_64 keywords, the hidden/blocked keywords, and all sorts of other complicated nonsense.]

More officially supported desktop environments/window managers than any other distribution:

Sabayon has something for everyone. In addition to their releases for the more mainstream   KDE,    GNOME,  and XFCE deskt op environments, they also support the following minimalist flavors: 

LXDE is geared towards low-end computers, shipping the LXDE Desktop Environment.

E17 is a minimal, CD-sized flavour made for people wanting to showcase the magic of Enlightenment 17.

Awesome is dynamic and highly configurable tiling window manager written in C and Lua.

SpinBase is a very minimal environment that can be used for many different purposes: didactical, home server deployment, but even for custom Sabayon ISO images creation, using their tool called Molecule). All Sabayon releases are based on SpinBase.

CoreCDX instead, is geared towards very minimal graphical environment setup, no fancy tools, browsers, whatever, just Fluxbox and command-line. You set the rule.

ServerBase is very similar to SpinBase, but powered by a server-optimized Linux kernel

OpenVZ is their official OpenVZ template.

In addition to their officially supported flavors, I have also successfully installed and ran Cinnamon, E16 (Enlightenment 0.16.x), Openbox, Fluxbox, Blackbox, IceWM, evilwm, i3, Afterstep, GNUStep WindowMaker, and hybrid environments such as E16 GNOME, E16 GNOME 3, E16 KDE, Openbox E16, and GNOME Openbox.

Sabayon uses all binary packages for repositories, but maintains complete compatibility with Gentoo's source-based .ebuilds and portage build system.

The beauty of Sabayon being built off of Gentoo is the provision of stable and cutting-edge packages, and a versatile package management system. Sabayon binaries, or custom-built Gentoo packages. The choice is yours.

It's fast!

Out of all the Linux distributions I've used, Sabayon ranks among the fastest. From the boot time to the responsiveness to the fluidity of multi-tasking to overall performance, Sabayon is king.

Resource management is amazing
As you can see in the screenshot, I'm running the Chromium browser with Google+ and Pinterest tabs open, doing a complete update of the system using Sabayon's equo command line package manager, compressing an archive of some of my most essential multimedia and documents, and playing music via the Nightingale (a fork of Songbird) music manager. All of these tasks are running smoothly on my 2 year old EeePC netbook, without any gaps in the music, and hardly any lag at all.

Solid native Sabayon documentation, and all Gentoo documentation is compatible with Sabayon
If there's one distribution that has truly peerless documentation, it would have to be Gentoo Linux. When I first got into Gentoo, it was the promise of being able to build my own custom Linux distribution completely from scratch (and by scratch I mean the original source code) using the wonderful tools provided by Gentoo. But what really got me into Gentoo, and what kept me going back to Gentoo's Wiki was their killer good documentation.

They have comprensive explanations on the purpose, use, configuration, customization, and repair of just about every Linux package there is, and the documentation they provide actually makes sense. When I want the barebones explanations, I use “man” (the command for the Linux manual). When I want a real explanation, I use the Gentoo Wiki.

Honestly, while the Sabayon documentation covers the most important documentation solidly, most of the problems I have (and you'll likely have) will deal with less important aspects of the user interface, like custom tweaks, unstable packages, and bootloader adjustments. So I'm generally relying more on Gentoo's wiki for Sabayon, but I'm sure it won't be long before Gentoo's documentation is ported to Sabayon's-- heck, I'll probably even do it myself!

Sabayon is beautiful
While there was even more apparently with GNOME 2.x and KDE 3.x (before these respective desktop environments became beautified), one of Sabayon's biggest goals is to be aesthetically pleasing, even in its name: the Italian desert “sabayon”, an Italian dessert made with egg yolks, sugar, and a sweet wine (such as Marsala). Like the desert, Sabayon is truly a treat for the eyes, with a beauty that courses through the whole operating system.

Sabayon can be unsavory though:
There are a few things that Sabayon needs to work on to truly be considered a “perfect” distro in my eyes:

1. Documentation: while Gentoo documentation is good, it's not optimized for Sabayon, and some major effort needs to be put into porting it to Sabayon, and organization existing documentation for better readability.
2. GUI package manager: Sabayon has been working on their package manager “Sulfur” for quite some time, and while the performance and stability of it has increased dramatically since a few years ago, it's still far from being competitive with Synaptic or even Kpackage. Sulfur should continue to be a top priority for Sabayon.
3. Bootloader configuration: Due partly to GRUB2, which IMHO is a nightmare to configure (much less customize), configuring Sabayon's bootloader have proved to be a royal pain, with custom tweaks to it all but impossible to accomplish. What Sabayon needs is better documentation on bootloader configuration (even Gentoo's documentation wasn't sufficient, sadly!), a Sabayon GUI configuration tool for the bootloader, and bootloader configuration support integrated into a system tools. The latter may be more of an upstream issue though.

Conclusion:
There are many many other ways that Sabayon reigns supreme as the absolute best overall Linux distribution project, but these are the main ones. As a compulsive distro-hopper who's seen just about everything Linux has to offer, I highly recommend you give it a try.