Just thought I'd chime in since I got a chance to try these on today!
First of all, MOST DEFINITELY true to size. It was already mentioned earlier in the thread a few pages ago that TTS is the way to go, and although I noticed a bit of length, it's perfectly fine to go TTS. 1/2 size up is likely gonna be too big, and 1/2 size small (like mentioned earlier) is gonna be too small. As they are built for casual purposes, you don't want any of the other two unless that's the way you rock your shoes, of course.
The Epic Reacts (when I tried it on yesterday) likes to hug your feet in. The Vapor Street Flyknits likes to chill on top of your feet. One thing I really like about it when I tried it on is the ease of slip-on and slip-off... it's so easy and so smooth. That being said, you definitely DO NOT want to try running in them. I mean, you can... but I wouldn't highly recommend it. From a birds-eye view, there's no React foam supporting the sides contrary to the Epic Reacts. The React cushioning is cool. Feels really good on feet... I'm not gonna get into the whole responsiveness part of it since it's a casual shoe, 'cause let's face it... I'ma be simply walking in these. Do we need that extra bounce when we walk? ****, I mean unless we're chasing for the bus... or chasing after someone who stole our phone, or laptop, or groceries... or you running away from the cops... damn, this **** got dark real fast.
ANYWAY, yeah, nice great casual shoe. True to size, go with that. Slipping 'em on/off is awesome.