I first tried using my 50mm Summicron Dual Range with the adapter, but found out that despite the pleasing low contrast look, edge sharpness was visibly inferior to what I had expected. I then attached my other M-mount lens, Carl Zeiss Sonnar-C 50mm f/1.5, and wow... I really like the tactile feel of this lens, and it looks like it was designed for X-E1. Quality-wise it's certainly sharp enough for me edge to edge, and works fine even without focus peaking by using zoom mode with X-E1 thumb roll. Bokeh is pleasing, and gives a slightly creamy feel to images taken wide open.
It takes some practice to focus manually without any assisting features (please Fuji, give us a new firmware with focus peaking), but I managed to take some action shots by relying on zone-focusing and experiences gained from rangefinder world. Here are some examples. I'll be using this lens for some time, as I had to send my XF 35mm for a warranty service. Front element was a bit off from the centre line of the objective body, and while it had no negative effect on image quality, the lens hood was misaligned when attached, and the markings on the lens were also off in front of the lens. Fujifilm Nordic promised to deal with this on warranty, so I thought I'd get it done before I really need the lens.
X-E1 and Sonnar-C
Perfect portrait lens?
Practicing zone focus