My take on it is that some people liked it a lot and some people got turned off by all the preachiness, then the internet did its ugly thing, everything got blown way out of proportions and now you mostly only hear from the most extreme people on either side. Though admittedly, the author having kind of an oversized ego and no people skills certainly didn't help.
Personally I very much enjoyed reading it, but more importantly, I like that it inspired a bunch of other authors to write their own pieces of rational (fan)fiction. Without HPMOR we wouldn't have had a lot of other stories that I greatly enjoyed/am currently greatly enjoying. Many of which are probably better (or at least more consistently good) than the story that started the pseudogenre.