i've thought about grabbing a kiev, mostly for the fisheye though i know it is something i would get bored with. if you do get one, read up on them because some are modded and some aren't, and there seems to be some differences between which lenses will fit. i found it all very confusing. i've read mixed things about build quality as well...but there is a big fan base for them.
you really only need one slr, as they are pretty similar. ends up being about build quality, lens selection and how it feels in your hands. i was a kowa six user for four years or so, but i like my bronica s2a better. it feels better to hold and shoot, and the lenses are very good and not as expensive as the kowa lenses. the 35mm lens i had for the kowa six was worth so much and it was so huge, i didn't want to carry it in my bag while walking around, so it wasn't much fun. the bronicas have a wide selection of lenses, as well.
great walls don't have interchangeable lenses. the lens comes off, but they only ever made one lens for it. you can tape other things on it though, but i don't find myself using mine all that much.
if you don't like what you get initially, you will probably go through a couple different cameras until something fits.
a couple shots from the S2A... you can see more in the review section. following up on leon's comments below about the sqa and the batteries, that is exactly why i went with the s2a. all manual (plus it looks a lot cooler).
