Let me put it this way:
The AT-Commandset is a (more or less) international standard. If the software is implemented well, there's no need to look out for what so ever.
There sure are other options available but those options cost money, a lot of money. I personally don't think that this investment would ever return for the Treo only (especially not since Palm announced to switch to WindowsMobile - for which I already have an working solution).
But here's the bottom line: If someone goes to "hack" some viable AT-Command Interpreter for the Treo, everyone will be happy