WeedMaps is OK. I used it to find every dispensary I've been to, which is about half a dozen because I'm new to buying medical marijuana. I take the reviews with a grain of salt, just like I take all reviews online, but so far I haven't been to any lousy place that had good reviews. Mediocre, maybe, but not lousy.
One thing I don't like is that some dispensaries don't post prices. I hope that trend doesn't catch on.