The hosting market is plenty big enough for more than one player - we're expanding to multiple languages, much like Heroku expanded from Ruby, which provides an ample feeding ground of old-style hosts to slowly steal business from - and there's also still a lot of room for innovation.
Heroku, as much as I like their product - and I do, which is why we started this a year ago - still has its flaws and idiosyncracies, some of which are those low-level-design type of choices where if you go the other route, a different set of people complain. You can't be all things to all people, and I don't think anyone will end up being that.