I've tried three different shift lenses so far. I have a Canon FD 35/2.8 tilt-shift, an Olympus 35/2.8 shift only, and a Samyang Canon EF-fit 24mm/3.5 tilt-shift. I tried each of them on Fuji bodies. I started with the Canon FD. Lovely lens, really well made, heavy and robust. An old lens so not bitingly sharp and colours are different to modern lenses. I found 35mm to be a bit too long on the crop bodies though. So I tried the 24mm Samyang when I saw one at a good price. Pictures from it seemed "more modern", contrasty and more saturated but the lens is huge, heavy and, more importantly, my copy had a broken shift mechanism so it went back. I've just bought the Olympus. It doesn't tilt (but I never used that in anger anyway on the other lenses) but it shifts in two directions at once, which I like - for stitching panos, which is my main expected use for the lens, I can shift up and take three pictures centred, shifted left and shifted right, then shift down and repeat (maybe also doing a row in the middle) and merge six (or nine) pics for a pano.
I'm in the middle of testing out the Canon FD and Oly lenses. IQ-wise they look very close with the Canon having the slightest edge at the moment.
This is a three shot vertical pano using the Canon FD (three landscape shots shifted vertically):
shard X by
Ian, on Flickr
This one is a six shot horizontal pano with the Olympus (not double shifted, just six portrait alignment shots shifted left to right with a lot of overlap):
National I by
Ian, on Flickr
Click through toFlickr and I think the full res shots should be visible.
If you are anywhere near north/central London you are welcome to come and try them out.