I now refrain from comparing Linux based distribution because what my needs are could be different from yours and what works for you may not work for me, but I am really impressed with Linux Mint in the 'out-of-the-box' experience department, it's becoming one of my favourites along with openSUSE and Kubuntu.
If we look at the consumer grade Linux-based operating systems which are 'factory' ready for a user, Linux Mint tops the chart, leaving Ubuntu and similar 'desktop OSes' behind. Whether it's MP3 or MP4 playback, everything works out of the box. It comes with all the drivers and codecs that one needs -- just download the appropriate version of Linux Mint. Due to this ease of use Linux Mint has become one of the most used distribution among the people I know. Unlike Ubuntu which keeps its business goals in center and want users to change and adopt, Linux Mint keeps its users in the center and changes the OS accordingly.
This Ubuntu-based distribution has also showed how Gnome 3 can be extremely useful and customizable with few hacks and extensions. As and when needed, the Linux Mint team forked a project (if upstream was not ready to change) or picked alternative to give users what they wanted. Unlike Ubuntu, the innovation happening in Linux Mint is focused on users and not themselves. The next version of Linux Mint is already in the pipeline and Clement Lefebvre has updated the roadmap for Linux Mint 15 with focus on several components - Cinnamon, Nemo, MDM and Mint Tools.
Version 1.8 of Cinnamon is expected to bring further enhancements which include the ability for Cinnamon Settings to browse/install/remove/update themes/applets/extensions/desklets remotely. It also aims at 'merging' the Cinnamon and Gnome properties within the same setting tool - Control Center. They are also considering rework on Cinnamon 2D. As Lefebvre writes on the GitHub page:
Rethink Cinnamon 2D, fallback to a non-shadow CPU-less intensive session in software rendering mode and/or Muffin/OpenBox (whatever happens, the user should know he's not running the "real" Cinnamon, he should be told why, and he should find himself with a working WM (even a minimalistic one like OpenBox)).
In the eye candy department the team is planning to introduce configurable color schemes for themes, calender events similar to that of KDE and upgrade Menu applet with mintMenu features (highlight new apps, install/remove apps, search the Web). They are also planning to add new applets for email notification as well as RSS feeds. The new desklets proposed are - system monitor, picture, video, slideshow frame and terminal.
Putting some sense in the file manage: Nemo 1.8
Gnome's default file manage Nautilus (now Files) is going through a major transformation and has been stripped from any 'useful' functionality, rendering it useless when compared with much more powerful file manages like Dolphin.
I still don't get the 'smartphonization' of desktop operating systems - but that's subjective. In my opinion KDE got it right -- they have all three form-factors covered - netbooks, tablets and desktop without any compromise on either. Linux Mint seems to be doing the right thing with Nemo by keeping alive the features needed on desktops.
The Linux Mint team forked Files and created Nemo. The team is planning some improvements with Nemo for the version 1.8. It will offer file preview and bring some UI improvements such as sidebar selection, independent path bar, better looking breadcrumbs etc. They are also planning something that Lefebvre calls, "Action API (reads desktop files in /usr/share/nemo/launchers. An action is basically a text file which defines a name, an icon, an executable and which file extensions nemo shows the action for when the file is right-clicked. A typical example of this would be a "Edit tags" action which would apply to *.mp3 files.)."
MDM & Mint Tools
They are also working on enhancing MDM and plan to add add a "border" property to "entry" objects so themes can get borders around text fields and write a new renderer which supports animations and interactivity to get on par with unity-greeter in terms of looks. Mint tools will get some UI improvements for Software Management as well as live installer.
All these proposed features look promising and will only enhance the user experience for a Linux user. If you have not tried Linux Mint yet, you can try the latest stable release code-named Nadia.