So far everything is excellent. This really, obviously is the finished ROM and not some leaked bodge job - everything runs perfectly, no hiccups. Linked and threaded mail is great, the facebook/twitter integration is flawless, fast app switching is great, and everything is faster overall. Even though I live in a fairly small UK town, local scout had a lot of good hits (looking forward to trying it out when I'm in London tomorrow) so very impressed with that - it's done much better than some dedicated apps I've seen. The new shutdown slider is nice as well, and IE9 is far more robust. Oh, and the colour banding is gone! Yess!!!
Hands down the biggest obvious change is in Hydro Thunder. I don't know what they did, but it's gone from occasionally stuttery to absolutely flat-out smooth. Hopefully this is the start of a lot more high-quality 3D games on WP7, as it can obviously handle them now.
Complaints? Just three, and they're really nitpicks to be honest. First - whoever decided the background colour for the task switcher should be your accent colour rather than just black or grey needs to be shot. It looks awful! Second - I do miss the fullscreen option in IE, but it's not that bad. Third - it's sometimes *too* fast. Those nice swoops when you click on a tile and open an app? Almost too quick to see now!