Just wanted to add my experience. I'm on Android, using Chrome (I tested on Opera as well).
- I can't login at all on the beta mobile site. I can login to the desktop site on my phone but the cookies don't transfer over; I remain logged out on beta.
- Trying to view any gallery in beta gives an error message about no pictures. It seems like pictures and videos on the desktop site work fine, although it takes a while to load them.
- as I'm writing this, I can't seem to load the beta site at all.
- sometimes, I can see a picture but when trying to see the gallery it's in, it says 'this has been flagged for review'. Refreshing usually makes the gallery visible.