The day to day editing remains on the surface very similar. So, there's no real learning curve switching/upgrading from 10 to 12. The most significant reasons are dependent on your computer system. If you have a 64 bit operating system, version 12 takes advantage of that. For the average user, the difference may not seem huge, but there is at least a noticible improvement in the application's stabiliity, response times and improved rendering times. If you have a fairly decent graphics card - see the recommended hardware list - this is where you'll definitely find the most changes for the better - especially for the preview window and some higher end rendering settings (not all settings can or need to take advantage of this). I mean, I don't know your budget and we can't see your system specifications because you haven't filled them in on your user profile (hint, hint), but my general opinion is:
The price isn't high at all - and there are often 15% to 25% discounts poppping up from time to time - so if you're using the application regularly, don't wait to upgrade.