The thing thats going to attract most users is increasing the amount of coins on the pool (particularly with new coins that are highly profitable) and increasing bth/mh.
Right now we only support Cryptsy so we're a bit limited by that. Cryptsy has been really reliable for us and I can hardly imagine using other services because they are all so fucking sketchy and lack APIs. Coinedup has no APIs, Vircurex is way too sketchy, coinmarket.io has no trade API and once again, sketchy as hell. You can't even find out whos running some of these exchanges.
We make tweak how our BTC/MH is calculated because other sites show the BTC/MH depending on only accepted shares which would inflate our rate a bit.