"Great keyboard, but you need to ditch the stock ROM"4.0 starson by metatr0n
Pros: Keyboard!!! Wonder, clicky keys, widely spaced!
Easy to unlock and root.
Small but very active hacking community.
Lots of alternate ROMs.
Extra hardware buttons.
Cons: Mediocre battery life.
No flash for mediocre camera :(
Stock ROM is not very good and loaded with bloatware that slows down the phone.
Summary: For me, the great hardware keyboard overshadows the middling hardware specs for this phone. Overall it's a good middle of the road phone, so long as you ditch the buggy stock ROM. Fortuantely, there's several good ones out there (a shout out to Platypus dev team, ayoteddy and sdivuck!). I'd recommend glorious overdose.
The sound/call quality is extremely good as well.
For tech types who do edit files on their phones or for anyone who types a lot (emails, etc) this is without question the phone for you. IF you're looking to play lots of games on a huge screen and enjoy a tablet-esque multimedia experience with tons of eye-candy you definitely need to be looking elsewhere.
I've given a more comprehensive review on my blog at http://www.nirdvana.com/2012/01/15/review-samsung-sidekick-4g-t-mobile