People tend to love him or hate him. I personally really enjoy his style, and if you treat the books as something less than "horror" per se but just "weird fiction" (which you mentioned), then the expectations are somewhat different. There is a bit of predictability in some of his works, but I don't have a problem with that. I think that much of the credit he gets is probably due to his influence on other writers, as well as on movies, music and other arts.
ἡ δὲ κἀκ τριῶν τρυπημάτων ἐργαζομένη ἐνεκάλει τῇ φύσει, δυσφορουμένη, ὅτι δὴ μὴ καὶ τοὺς τιτθοὺς αὐτῇ εὐρύτερον ἢ νῦν εἰσι τρυπώη, ὅπως καὶ ἄλλην ἐνταῦθα μίξιν ἐπιτεχνᾶσθαι δυνατὴ εἴη. – Procopius
Ummaka qinnassa nīk!
*MySmiley*