One big downside for me is not being able to order from mobile. As in, it's not possible.
That's not a huge deal, though, and it's understandable considering the website is relatively new.
There are a couple things that file under "minor annoyances" but my one big issue was today:
I'm on my phone, by some miracle found a pair of slim-straight indigo in 28. I put them in my bag and go to check out. I realize I can't enter my state since the scroll-down windows (idk wtf...