I love mine too, it's so light, and with that lens just awesome. I little quirk to look out for is that it doesn't measure TTL, it measures TTF, through the finder. Because of that you need to be very careful when shooting landscape with a bright sky, especially with slide film. You can use EV from -2 to +2 but you have to remember to use it. I'm not that thoughtful -_-
On the plus side, having put over 80 rolls through mine now, I can load it while standing up, the loading mechanism is quite thought through. When the back is open, the wheel on top is used for turning the take up spool, you just put the backing paper in, scroll ahead a bit, then close the back, the camera senses the beginning of the film using an infrared sensor if I remember correctly.
Quite a lot of pictures on my flickr stream were made using the GA645. I don't care about the noise, which, to be fair is quite lets say nasty, the quality of the lens is sublime.
Oh, another thing, wierdly, the GA645 only puts 15 shots on a roll of 120 film, the GA645i manages to get 16 frames per roll. Noone knows why.
Another big upside is, having a leaf shutter, you can get a shot using half a second of exposure time, although you are a bit limited speedwise.
For me the GA645 is perfect, I often ride around on my bike and being able to put a medium format camera with a lens like that in a small pocket just is the bees knees.
cheers