If you find hard to type long passwords in your touch devices, you may get relief soon. Gnome developer Giovanni Campagna is currently working on a PIN unlock feature, similar to mobile phones, that is aimed at being touch friendly replacement of passwords.
The feature is complete and waiting for review to be included in gdm and gnome-shell codebase. Sadly, it wont be included in Gnome 3.6 due to stability issues.
Here is a screenshot of how the unlock screen may look like:
This feature is meant only for local logins. You can read Campagna's blog post here.