Hopefully this will be of some use to you mate: I got the update today and after about half an hour of screwing around everything seems much smoother. Update automatically turned off USB Debugging Mode but there's no apparent lag, so I guess that issue has been fixed. They've made a few nice changes, now the app screen scrolls a page at a time and there is now a "Quick Settings" tab on the notifications window which lets you toggle Wi-Fi, Bluetooth, Wi-Fi Hotspot, GPS and Mobile Network. Aside from that and a few new menu options, there's not much else to see, but I should imagine there's a lot of stuff going on in the software that you're not necessarily aware of.
HOWEVER: I did see a few posts in the forum from people who have had problems with the update. One said that Wi-Fi wasn't working any more, another said that their phone had been eating the battery since the update. I'm guessing these are rarities (though I did think twice before updating), you should be fine, but be aware there is a minor risk there. It sounds like you have just got your phone though, so if you update and it does something funny, I guess you could always try a factory reset and go back to 2.2 without losing too much stuff.
That's just my thoughts on the matter after a few minutes observation, perhaps someone else would like to weigh in?
