Fuji makes an excellent system with IL already, only thing lacking is decent AF speed, sure the the firmware will make the X-Pro1 faster and same with the X-E1. No it isn't full frame, but what a great sensor. Lenses are decent in size. Now the only thing to look forward to from Fuji is the next generation X Pro 1 hopefully in 2013 and if they can deliver in Speed, it will deliver a good balance in size too. I still feel Full frame cannot deliver in good enough size with lenses in the NEX system, and what they have done with the RX1 is technological marvel!
Full frame ultimately offers two things over smaller sensor 1) DOF, 2)higher ISO sensitivity (better signal to noise ratio).
However, the best the RX1 have gotten with the Zeiss lens is f/2, while taking nothing away, I expect it to be great! With APS-C lenses from Fuji, you can be sure you can overcome lens design by offering to make lenses slightly larger, and thus getting most of the central resolution without the burdening cost. This is always the philosophy of smaller sensor design cameras and they have already offered lenses with larger aperture of f1.4 at a great price point. At the end of the day it's a compromise.
The RX1 are for those who definitely want a the highest quality full frame in the smallest package, and it is as small as m43 Panasonic GX1. Seriously guys, you were never going to get it cheap (US pricing is reasonable)! (Although it is a shame about UK/European pricing)