Knowhere is an incredible card for Star Lord!
It compares to Avengers Tower but, for Star Lord, even better. Indeed, the + 1 ally applies to any kind of ally, not just avengers like the tower does. And while it does not help you pay for the ally (which shouldn't be too hard with "what could go wrong?"), it gives you a card, which is even better. AND since Star Lord makes every ally a Guardian, it works every time.
It will, however, be far less impressive with other heroes. First, it's only playable by the few Guardians we have so far but, more important, they do not share Star Lord's "turn everyone into a guardian" ability.