My brother had a GF670, and we both thought it was just superb. It's only fault in my eyes is the fixed lens, which for me is no big deal, but he wanted a wider angle lens.
I used to have a Mamiya 7, which is a fair bit bigger than the GF670 as it does not fold up, and I did not like the build, but the results are not in question, you've got a choice of lenses, and it's all round pretty nice to use.
For older models, I like the Zeiss Super Ikonta III.
If I was buying myself a present, the GF670 would be way up the list, I think it's one of the finest cameras around at the moment. If you wanted wide angle lenses, I'd also look at the Fotoman Dmini. I have had the Fotoman 69, which is similar, and it's a pretty compelling camera if you want very wide angles on medium format film.