I think it was mentioned earlier in this thread, but people should really give "PocketCM Contact" a try. It is a normal install - no overwriting files or getting into the registry like that Palm hack. It is FREE - which was my main interest.

It is a bit funky - you have to click and hold the SEND button for 250ms to send a message. The developer says that is to prevent accidental sends, which I admit I have had before. It also is useful because it tells you right away in the thread if a message doesn't get sent. With the default SMS app, I would have to go into Drafts and resend it - this feature alone makes it worth the install.

It is not perfect - I do have some complaints - but I have to say it is the best FREE SMS app that I have found so far.