Biggest problem is that most computers' USB 3.0 ports won't work without Windows Drivers. No machine I have ever worked on (which totals to about 40-50 in this past year) that needed an OS reinstall could do it through USB 3.0 ports.
Every time it wouldn't recognize the USB stick or boot from it. USB 2.0 ports, however, worked just fine.
USB 2.0 is better than DVD, that's for sure, but not incredibly so. Find yourself a good USB 3.0 stick so that when standards catch up and you can boot from them on most computers you'll be ready.
I have one of these
and have been quite pleased with it. It's pricey for whatcha get though.