Speaking only for the X-T1 (update: looks like the new 1.16 firmware fixes issues with X-E2 and X100S but I haven't tried it in the field) - If you already have Canon 600 EX-RT flashes the hot setup is to use the Yongnuo YN-E3-RT. It doesn't allow TTL but does allow remote control over flash power. I've tried using my Pocket Wizards (TT5 and TT1) and just don't get the same reliability as with the Canon setup plus there is no extra equipment on the flash side which simplifies things a lot when you're placing strobes into locations you don't have easy access to. All you worry about is mounting a flash and making sure you have battery power to the flash (and can use external battery packs for the flash).
Not a cost effective solution for people who don't already have the 600 EX-RT, I'll admit, but it's a high quality reliable solution and the 600-EX-RT is a very durable flash (much better than the 580 it replaced)
Note the one (minor) unfortunate feature of this system is that you have to hit the test button on the Yongnuo after any power level change so it sends the new power level to the flashes (unlike the canon E3-RT which just sends it automatically). Beyond that it just works and works just like the Canon controller (at 1/2 or more off the price)
I suspect the Yongnuo 600-EX works instead of the Canon flash but I haven't tried it. It's also clear from reviews that it isn't as durable as the Canon and that durability may be worth 3x the price to some (it is to me, who wants to work through a problem while on a time critical event like a wedding or music event?)
Still waiting for a TTL solution FUJI! I just wish they'd hookup with Yongnuo and be done with it. Maybe they could get Yongnuo to bump up the product quality a bit while they are at it.
Update: I just updated to the latest 1.16 firmware and there is a new "legacy trigger" mode option that appears to have been added specifically for Fuji. Turn it ON. With that I can now trigger my 600ex with my X-E2 and X100S. That said I haven't used in the field so can't say it works fully but am guessing it will now.
