I have a pay-as-you-go plan on T-Mobile, and they charge $0.10 each for a text going out and going in (last i checked). So I really hate texting on that phone, since a conversation can get really expensive, even one that's two or three messages long. I also hate typing on a T9, but sometimes I just have to use it because I get service everywhere, and I can't get Wi-Fi everywhere. If I did I'd use Textfree on my iPod touch exclusively.
Unfortunately it looks like iMessages can't solve that problem and I'll still have to rely on carrier SMS when I'm not on Wi-Fi.
Unfortunately it looks like iMessages can't solve that problem and I'll still have to rely on carrier SMS when I'm not on Wi-Fi.