Mobile app? I've only accessed Steemit on mobile, though the esteem app has never worked for me, I use it in browser.

I hope they add the same in app video support as they have for photos.

I'm interested to see what communities does, but can't figure out if it will start pigeonholing everyone or simply simplify finding common thinkers?

Definitely think now is the time for minnows to grow, whales are cashing out to drive the price down for the next buy. A low steem keeps the leeches off the field, reserving it for people who would be here without dollar incentive, then when the next bull run comes, those people will succeed the most.