I'm not on the G2 (epic4g), but the lack of a spell checker in android is also driving me nuts.
Predictive text is not the same thing as a spell checker. Personally, I just don't like the way it works when typing out an email on a physical keyboard.
However, beyond my preferences, I've heard the predictive text argument so many times I thought I'd just chime in with one concrete example of when it fails.
I work in a professional biological research position and use a pretty hefty amount of acronyms, which are often quite close to 'actual' words. Furthermore, as I go from project to project (and sometimes even within a project), those acronyms change on a monthly (or even weekly!) time frame. In a situation like this, predictive text is a nightmare. It is constantly changing things, which in this context can drastically change the meaning of the email, rather than just be a noticeable spelling or grammar snafu. On the other hand, it is decidedly unprofessional to send out emails with spelling errors.
So perhaps you can see the problems some of us have, even if it does not affect you personally. I've posted this same request to Google's site, but since they have been ignoring it for years I'm not terribly optimistic.....