I didn't even consider it cheese (well maybe the dozens of simultaneous doses bit, but not the conjuring itself). Poison is pretty craptastic past level 5 or so, because the save DCs don't scale and it gets horrifically expensive to use it consistently. I may bust it out one in a while for some sort of defensive purpose because I'm innately immune to poison (and it's free, even if it only lasts an hour), but it's only practical as a holdover until I have more than single-digit power points.