are you thinking of picking up an eris? id recomend it,you can find them cheap now,and have a lot of fun rooting and ROMing.
i had an ally for a week or so... i sent it back cause it was so terrible. it was laggy and glitchy,and force closed apps constantly. i hope 2.2 and the ability to root and remove some bloatware has improved its functionality.
as far as 2.3,some of us are using tazz gingerbread,but most seem to agree worksheds version "gingershedbred" is the more stable of the 2 at this point. i wouldnt mess with kaosgingerbread until some more updates are done on it.
all the froyo roms are based on CM6 ports from the hero,and allow a great degree of "tweekability". i could recommend about any of them,really. if you want a funky themed rom,try worksheds "froshedyo v10","red glass" or any of his other themes froyo roms.
if your fancy is a simple,pure CM6 try CELB 4.3.
there are curently no completely functional sense-based 2.2 roms,so if youre a sense fan,youre stuck with 2.1 for now. maybe forever-i havent seen updates the the existing froyo/sense roms in quite awhile.
i did a benchmark test on gingershedbread,and it dint score as high as CELB froyo. i forget what the numbers were... 700ish for GSB and 760ish for CELB. both tests with the processer OCed to 710.
my 2 cents,anyway.
im sure there will be some other opinions along soon. we are lucky to have some devoted developers to provide for our "little phone that could"
last and not least,some more info and links in this thread here(wich is a few down):
http://androidforums.com/eris-all-things-root/281627-eris-roms.html
edit: just ran another benchmark test. here are the numbers if youre interested:
gingershedbread
memory: 93
CPU integer: 191
CPU float: 16
2d graphics: 149
3d graphics: 70
database IO: 30
SD carw write (3.1 mb/s) 31
SD card read: (13.4 mb/s) 134
total scores: 714
for SH*Ts and giggles,maybe ill relaod CELB and run it again
CELB froyo
memory:75
CPU integer: 221
CPU float: 18
2d graphics: 172
3d graphics: 88
database IO: 20
SD carw write (3.2 mb/s) 32
SD card read: (15.6 mb/s) 156
total scores: 782