It's not just the keyboard but they've also integrated hardware with the social networks as well. For instance it has a dedicated button for login to FB. Other things like live updates of what you're friends are up to, news feed back, share photographs are also there.
The the phones looks a lot alike the Blackberries to be honest and the slightly curved body might help while typing or is it not??. Anyway the screen is a 2.5 Inch one with 480x320 resolution (the ChaCha model).
Tthe Salsa on the other hand looks bigger in comparison, has a 3.4 inch screen with the same 480x320 resolution. So the ChaCha should have better looking pictures (slightly). They both come with 5 MP cameras as well.
Source: this pcmag mobile congress htc news article.