I just finished my 14 day trial of SMS-Chat by
http://www.iwindowsmobile.com/. The program works well and is very Touch friendly. All of the applications at that website seem to work well, especially with the touch, including a launcher and contact manager and keyboard. These apps, although they're well designed and look very nice, lack one thing in my opinion -- configurability. They do what they're designed for well, but I find they don't fit my need in customizing my device the way I want to.
My only big problem with the SMS-Chat program is that it stores it's messages in a new folder off the text messages folder. Because of this, SMS message counters don't work the way they're supposed to.
Because of those issues, I'm now trying out SMS Client from
http://www.pocket-sms.com/. I haven't had much time to test this out, but if it's not amazing, I'll be purchasing SMS-Chat.
Hope that helps with 3rd party apps.