Things Ello.co should make use of to assist in their growth.
Opengraph protocol processing. Like it or not, it would be stupid not to incorporate it. It's readily available and in use by the majority of the web already. Don't try to re-invent the wheel. Like it or not, that wheel actually works pretty good.
Better method to search for friends. It's a bit ambiguous to goto the "discover" area to do a search. Why not have a direct search?
Various themes. Currently, ello.co looks like a really bland version of.... well of LiveJournal. Until things like OpenGraph get implemented and made use of, the system really is going to seem a LOT like LiveJournal. A dead blogging system.
Wait, it's not dead? Oh well then, you're really doing something wrong at this point. ello.co, you've got a lot going for you at this point with all the "no ads" buzz that you've generated and pushed viral. So take advantage of your time in the spotlight to really shine instead of fizzle.