Most phones today are just fine for texting. One can become very speedy once familiar with the T9/predictive text feature. It takes a few days to get your legs, but once you're used to a phone, you're off to the races.
I personally use a BlackBerry Bold, and I love it. I used to have a T-Mobile G1, and it was awful. I tend to stay away slider phones, simply because they always wear out over time. I've had 2 Berries, and I will never go back to anything else.