Sonnar lenses, of which I have a ZM C Sonnar, a Rollei Sonnar LTM, and a Nikkor 85/2, all do very very well on the X-Pro1. The small amount of smearing at the edges just plays naturally into the characteristic sonnar fade from bitingly high resolution on center to sluggish resolution in the corners.
On the wide end, I've especially enjoyed using the Leica Elmar 24 with the X-Pro1 EVF. Results from the ZM 18 are almost as good, but the ergonomics on the smaller lenses like the Elmar is better.
It is easy to focus using the EVF, and relatively easy to focus and recompose toggling between the OVF and magnified EVF view. The Fuji M adapter has been a worthwhile addition to my X-Pro1 kit, and I'm glad I waited for it. Just too bad that I can't use the Nokton 35/1.2 on it.
Semilog gets it right when he says that for most pictures, the corner smearing isn't a big deal. I'm taking the X-Pro1 backpacking next week just to see how I feel about using it for landscape.