Rovio (guys behind the Angry Birds) published the list of handsets that they do not support for the performance reasons. I guess this is a good list and good argument to exclude those handsets from your future games and apps, unless you have a really serious reason for not doing that:
Droid Eris
HTC Dream
HTC Hero
HTC Magic/Sapphire/Mytouch 3G
HTC Tattoo
HTC Wildfire
Huawei Ideos/U8150
LG Ally/Aloha/VS740
LG GW620/Eve
Motorola Backflip/MB300
Motorola Cliq/Dext
Samsung Acclaim
Samsung Moment/M900
Samsung Spica/i5700
Samsung Transform
Sony Ericsson Xperia X10 mini
T-Mobile G1
And in addition to that they do not support Android OS below 1.6 and custom mods.