I'm right around 175MB too, but for me that's too close for comfort. I don't want to worry about hitting 200MB one month. If they offered 500MB, or 750MB I'd certainly get that.
Going over the 200MB plan isn't such a big deal, as long as you don't go waay over. I'm in the same boat. On average, even with the occasional overage I'll probably be spending less than I did with the $30 unlimited plan.