So far I've noticed quicker Wifi connection (for me it was like a half sec, wasn't an issue before), better GPS (I finally saw a (8) in the GPS field on google maps), fixed the browser input bug, overall it feels a little snappier. I haven't checked the photo quality yet, but I can't imagine the quality going backwards.
Kinda off topic, but Truphone finally officially supports the N85 (it worked with 4.0 for me, they seemed pertrubed when I was able to get around an register it... but 5.0 is official for the N85)