Side mirrors are gone! Took me 15 minutes tops. For the exterior, I cut two triangular cardboard pieces to fit and covered them with an almost stealthy black tape. Inside the cabin, we've got two handy little suction cupped mirrors on the windshield.
Afterwards, I took a deserted highway test drive. On the way out, I used P&G from 20-40 mph and saw 47 mpg. Coasting down from 40 to 30 seems to take a second or two longer, but 30 to 20 seems unchanged. Coming back, I drove a more-or-less steady 45 mph and saw 52 mpg. No official results or percentages, but I'd say a decent improvement overall.