Just received these in the mail and two things stand out:
1. The fit and finish is superb
2. They look much better in person than they do in photos
I tried them on, and the materials are nice and supple - they fit like a glove.
I'd heard rumors about them having a "wide toe box". Unfortunately, they are pretty standard cycling-shoe width, which is fairly narrow. I wear a D-width dress shoe and my feet hang over the sides of the carbon soles on these. I ordered a size 46, and the sole measured about 96mm at its widest point. In comparison to other brands, these are as narrow as DMTs, Giros and regular Sidis. Specialized S-Works (2013, regular) are slightly wider, and Shimano R170s (regular) are even wider still. Those with wide feet can squeeze into the R3s because of the supple upper material, but you'd be more comfortable in something wider.
I wear a 46.5 Sidi Genius 6 Mega, and they are a little roomy for me in the toebox (not the forefoot). I was told to size down 0.5 for the R3s, but I think I should've sized up to a 47, because the R3s were also slightly short. Even the few mm of width that extra size would've given me still wouldn't be enough to make them comfortable. Oh well...
As for the sizing questions - it'd be great if Competitive Cyclist and other websites would start providing some actual measurements for their shoes. I'm sure it would prevent a lot of returns, and the lasts probably don't change much from year to year.