I have an Arca-Swiss 4x5 Field C, which I bought last year. Its a great camera, one which I will never sell or trade. Its rock solid and very smooth. I have carried it all over the place in a photobackpacker custom case. Its a great camera. I use it with a variety of lens from 47mm to a 450mm, and it handles them all very well. The only thing I wish I had one was buy the telescoping rail. I have the 30cm collapsing rail & a 25cm extenstion rail, which is slightly bulky comapred to the telescoping rail. I have used it with a Horseman 6x12 back & a friend's 6x17 back, it preformed perfectly. I did keep a light weight field camera for long hikes, where the Arca is just a little too heavy/bulky.
You wont be disappointed, if you have any questions I would be happy to try to answer them.