Well, I've noticed two apps not performing well at all so far on 2.2.
Pandora: Sounds very tinny now...much worse quality with froyo (yes, I have high quality checked under preferences and always have)
Cardiotrainer: GPS cut out for over 2 miles of my jog. My GPS has never cut out before on any trail including the one today which I frequent (or using Google navigation in the past). I'm not sure if it just happened to have a weak GPS signal or the program itself performs shoddy under froyo.
So it sounds like my initial fears regarding the froyo update have come true.
Worse GPS strength and crappier quality Pandora! I wish I hadn't updated!