I'm a big fan of the i40, it's not as solid as my Nikon speed lights were but it does what I need so far.
Though I still have a Nikon set up too for off camera flash work, this is set to change once the new i60 comes out (I'm hoping to get a sample copy to test) and I have tested the commander and receiver system that nissin are putting out. I have the Nikon version on the way to me now, the Fuji is yet to be released I believe.