Eye placement is more critical with the 35mm IME. On the few occasions I tried it I found it awkward to use compared with the 27mm. (But I did own a 27mm Pano though so I was more used to that.) A couple of Televue eyeguard extender should help with that though.
If finances allow, I second Geoff's recommendation of 30mm XW. Brilliant. Has Panoptics for breakfast.