I got upgraded sometime last night and I have to say, I'm happier than I expected to be. Can't help with other folks questions, sorry.
I still hate the amount of screen space wasted by the guide (both the fact that it isn't wide screen and the amount of space that isn't used effectively) and the fact that you can't see more channels at once. Also the lack of different color schemes makes the low contrast of dark blue on light blue of highlighted channels in the guide sorta weak. Not great for folks with poor vision, luckily mine is ok. Oh and I do wish I could just disable channels I will never ever watch (shopping channels, certain news channels, etc.).
Overall I like the new interface. I like the Access Menu. I like being able to find search shows by category, etc. I like being able to make favorite channels show up at the top. The interface seems faster over all. It's nice that you can see how full the hard drive is now. (Maybe you could before, but I didn't see it.) It shows when shows start/end more accurately. There are a ton of nice small tweaks. Overall, it's a step in the right direction.