I've been wearing vivobarefoot shoes for several years now. They're all I train in (25-35 miles a week). The old neo trails were roomier and flexed better on toe off.  These rub my large toe when the shoe bends, so I'll have to use them with socks, and will struggle with comfort on longer runs. Luckily, I still have quite a few of the old Neo Trails lying around that I can use for longer runs until I can find a better shoe.