Ordered these about a month ago, and I am a fan.  The shoes are very comfortable, and are a nice, casual summer alternative to a flip flop or sandal.  They are a bit warm, but that was expected, as they are basically an enclosed flip flop of sorts.  They do have the vents on both sides, and that definitely does help.  My feet don't get sweaty in them, just warm.

As far as fit is concerned, I would say they are true to size and will stretch a bit.  I am a 10.5 and ordered an 11, and they are a bit big after they stretched (big as in roomy, but still fit snuggly at the opening), but not too bad.  I could probably have ordered a 10 and been good with that as well after the stretch out period.

The one true negative I have is that the fabric stains quite easily.  It can be cleaned, but if something is going to leave a stain, it will.  Spilt a spot of ketchup on the side of one, cleaned it almost immediately, but it still left a small stain.

12/2013 Update: I had to remove a star from my original review.  These shoes are, honestly, not worth the price.  First, the apparent "anti-microbial" treatment does nothing to help the odor that builds up in these enclosed shoes.  Found myself using Goldbond powder in them just to absorb some odor, even after just a few months of owning them.  Second, the sole of these shoes, basically being foam flip-flop material, wear down quickly.  By the end of the summer of 2012, the pattern on the bottom was already worn flat on the heel and ball of the foot (after wearing them sporadically, maybe 2-3 times per week with light walking).  I kept them and wore them a bit this past summer as well, but predominantly stuck with flip-flops as my go-to footwear.  Even with the limited use, they wore even further and have been trashed.  In short, it was $60+ for glorified flip-flops that didn't even last two seasons.  Won't be purchasing Sanuks again in the near future.