I received the kit (with 16mm/2.8) yesterday and after charging the battery, mounted my ZM Sonnar 50mm using an adapter I bought from "jinfinance" on ebay. The fit between the adapter and lens has a little play, but nothing to worry about.
Size-wise, the Sonnar doesn't seem overly big when mounted on the Nex5. Using a wrist strap, I cradle the kit in my right hand and manually focus with my left. Yes, I said cradle -- the Nex5 is so small I can't hold it like I would another camera body. Also, since I am focusing with the LCD at an oblique angle, pressing the shutter button with my index finger is awkward, so I press the shutter button with my thumb.
As to usability, the reported jumble of menus is not really that bad. It's actually very intuitive, and the approach Sony-Ericsson has taken lends itself easily to firmware upgrades (perhaps for future customization?).
The 7x or 14x magnification manual focus assist is very nice, although that much magnification does make it obvious that my hands aren't as steady as I had thought they were.
I don't have any pictures of the kit itself (cameras are for TAKING pictures, not posing for them), but here are a couple:
These are straight from the camera -- did NOT go through Photoshop at all. Shot at AWB, jpg = Fine. Both @ f1.5 (my Sonnar is optimized for f1.5) -- the first is at the minimum focus distance of .9 meter (focus on BLUE warning label), while the second is from roughly 4.5 feet away (focus on the RED handle).