I, too, sometimes have a lag when I'm texting, but it doesn't really bother me. I'm a very fast typer, so I'm used to having things slower than I am
In addition, I often have a lag with my contacts, but its not anything that really bothers me. Okay, so sometimes it gets annoying....but overall, I have no complaints.
I'm sure it will be fixed with an upcoming update.
I really hope they can fix this lag in the next update. If anything, the texting lag happens more on my 2.0.1 iPhone 3G than it did when I had 2.0 on my V1. Its really annoying since I like to text a lot and fast.
Go to General - Keyboard -international keyboard, leave english on and turn on english(uk). Got that from another foroum and it helped. Not a solution but i temp fix till they update it. It worked for me. If you don't want to do that, open up safari and hold down the home button till safari closes. That will speed things up also. I think the first opt is better as i am always on the internet.
And yet another crappy solution (to this problem that Apple should be fixing, but they aren't because, oh, who knows)... is to put the cursor in the middle of a word and go from there. This appears to wig-out the spell-correcting logic and allow you to type fast again. This seems to have something to do with that auto-correcting program... maybe if they had a way to turn that off, it would solve this particular issue...
My biggest lag issue is when you enter a text conversation, and you hit the bubble to start typing. It lags anywhere from 2-7 seconds to bring the key board up. Once it does its rather zippy and keeps up, i just get on occasional "half click" when typing.