I noticed that with a few of my contacts, whenever I call them (from the People app contact card), it tries to setup a 3-way call with the same person... I only press the "Call Mobile" button once though... Putting a shortcut directly to "Call Mobile" seems to alleviate the problem.
So some parts are buggy...
Navigation is good, could be a bit better. I noticed that it doesn't always say the turns to take for some reason... Or it'd say them far in advance, and say nothing when you get there.
For those on 1.5, Waze is still a good app, but there are some parts where it takes you down strange routes or the wrong way... So on 2.1, Navigation is a lot safer in areas you're unfamiliar with.
Running the GPS seems to take more battery on 2.1 then it did 1.5 (without any gps apps running). On 1.5, I never turned off the GPS and could make it through the day, on 2.1 the phone makes it through the day, but it red lines (the battery bar gets really low). Turning off the GPS fixes the issue, but I like it on for GeoTagging photos... Looks like a new battery is in question...
The GPS also seems to locate you a bit slower than on 1.5, or maybe it's just me...
Multi-touch on 2.1 seems more responsive, but it changed from 1.5. On 1.5, I could just pinch and whatnot, but on 2.1, I need to put on finger down, and then do the gesture with the other finger.
I actually thought Leap was pretty useless at first, but now I find myself using it more and more (maybe because I'm getting widgets I actually use). So if you like using widgets and jumping between them, it's cool.
I'm personally really happy with 2.1. Made my friends jealous (not the only reason I'm happy). It's a lot more responsive, and other than the issue with calling about 3 people, I don't have any "Oh Why God!?" issues with it (it became an "Oh why god!?" issue when I'm asking for directions running 5 minutes late, and they say "Now go to..." and then I hear ringing and it's trying to 3-way call the same person and we don't know how our phones work
).