I remember there were announcements, that Ubuntu Software Center should get a rating and review system. Don't know if these announcement were official, but I remember it was stated it could start before Christmas. What's the recent status of these new features?
Ratings and reviews have now landed in the current development release of 11.04.
Keep in mind that, normally, no major updates are performed within one release. In almost every case, updates are "Stable Release Updates" (SRUs). But see the second part for what will hopefully be an exception in February. :)
(Image by omgubuntu)
Software-Center's Launchpad Project page also has instructions on how to try the latest development version, if you want to check out what's currently going on:
This is experimental, unreleased software. If you do decide to try it out, and you encounter a problem, Report a Bug - after making sure it hasn't been reported already.
The ubuntu software centre in Maverick will get ratings and reviews in February 2011, according to it's page in the Ubuntu Wiki
Many thanks to @NES for keeping us up to date on it!
Ratings and reviews will appear in 11.04 which will contain version 3.2 of the Software Centre.
However the blueprint says that version 3.2 with Ratings and Reviews support may be officially released as a (compulsory) upgrade in version 10.10. If this does happen it won't happen until at least the end of March.
In the meantime Stefano rightly says you could try adding the ppa, however there is a bug that prevents the ppa package from installing.