I just finished upgrading my ADP1 to Donut. The icons and such look a little more polished, and supposedly the new Google Maps supports turn by turn. If the new Google Maps app works well, I may pick up a phone mount accessory for my car.
Since I use the AT&T pay as you go plan, I also needed to update the Phone app to ignore the "last transaction" messages as I did with cupcake. For those of you that are interested, you can download the modified source and compiled apk:
The instructions are the same as for cupcake, so see my earlier blog post for instructions.
I have recently tried CyanogenMod on my ADP1, and this patched Phone.apk has been working fine.