I tried chomp, handcent, go sms.
My opinion is:
1) Go sms
2) Handcent
3) Chomp
Go sms saves everything, it's smoother than handcent, very customizable, there are several themes for it if you are into that.
I actually liked GOsms so much, that I ended up getting the launcher. I never thought I would change launchers on my TB. The launcher is smooth, but there are some things about it I don't like.
As a text messaging client though, Go is the best!
I'll have to give go sms a try. The stock app locks up on me, I had Handcent for awhile but it started randomly losing about 50% of my messages. I'm using Chomp right now with no issues, I like it better than handcent.