I installed today Office 2010 and I must say... it is much better than 2007.
At least PowerPoint is, I used it the most... It has great new features... a new rendering engine, so animations are much smoother, also I see the text is antialiased, looks better than 2007. And I think I saw some motion blur as well, but not sure about that one...
Also some new transitions are available, improved 'text' and 'shape' effects, also some nice image effects like color correction, blur, water ripples etc...
Video and audio have now better support, also player controls, and I think it uses QuickTime to render video (some formats I think).
In word I found now available text effects, that weren't in 2007 (like the ones in powerpoint 2007)... haven't used it a lot to say more.
I didn't have problems with the RAM, it works just fine with my 1.5 GB (and windows xp). My old PC handles it just fine. The installer took a record time to download and install, the installer for winamp (just an example) is slow compared to this one... I was impressed.
I also found some bugs, but it's still beta, right?