I like the lighting on _u12. It's a definite improvement for visibility. I also like the switch to nonsolid eaves. That said, _u12 has a lot of issues that either weren't reported or weren't fixed from _u10.
On RED side:
Old Issue: the the left corner has some ugly overlap between the roofs.
http://i.imgur.com/slEGwqP.jpg
New issue: the eave over Second-Saw is solid. You can get caught on it when jumping up and even stand on it.
http://i.imgur.com/ZH6J2wi.jpg
New issue: the eaves on Mid are solid.
http://i.imgur.com/bOIK5Uv.jpg
On BLU side:
Old issue: you can stand on the boiler in Lobby. It's not a wallbug; there's a lip you can walk along.
http://i.imgur.com/EK2AYTb.jpg
Old issue: the clipbrush above Catwalk protrudes past the wall.
http://i.imgur.com/vZoieIx.jpg
New issue: you can stand on the eave above the wall vent at Mid.
http://i.imgur.com/yVbEBC4.jpg
New issue: the eave above the Saw-Mid is solid and can catch jumping players.
http://i.imgur.com/kvWEaWz.jpg
On both sides:
Old issue: you can stand over the door at the Second-Saw connector.
http://i.imgur.com/lGqgAyR.jpg
Old issue: the following eaves are solid:
http://i.imgur.com/U0OsRWv.jpg
http://i.imgur.com/pSlIEOn.jpg
http://i.imgur.com/ByHLKM4.jpg
Old issue: the lights shine through the log on Train. I forget if this was a Source engine bug or not.
http://i.imgur.com/8IVye1m.jpg
New issue: it would be nice if the corrugated metal were on top of the roofs at Mid, instead of hanging underneath. It's unclear where the roof is nonsolid and where it's solid.
http://i.imgur.com/IXkRGOr.jpg
New issue: the Shacks are inconsistent. The ones at Mid have nonsolid eaves, while the ones at last and the Tower are clipped off.
http://i.imgur.com/lFatAuI.jpg
http://i.imgur.com/z8NAjiJ.jpg
http://i.imgur.com/IvmjAPA.jpg
Due to the new hiding spots and other asymmetry, _10 is still more usable than _12. Thanks for putting in the work consistently to release updates! Snakewater's getting really close to perfect!