I went to a touch screen and I will say it did take some getting used to, and missing buttons is still a problem at times, and conditions, but I prefer it to having a non touch screen phone now, its just so much easier to use for many different things.
As for the G1 or the My Touch, I don't know that I could ever not have a physical keyboard, because every time I try to type with out it on my G1, I mess up half of it, and it takes me 3x as long, but thats a personal thing.