It was notoriously tough on PCs at the time (lighting system, mainly), and it was a departure from the classic boomer-shooter run-n-gun gameplay that the series popularized. Instead, it was paced more akin to a horror game. Personally, I think its a good game, but not a good Doom game, which ironically seems to be the trend with the third game of any Doom iteration (i.e. Doom the Dark Ages). Doom 64 is actually a more faithful take on the "original formula," but Doom 3 is still forward thinking in al ot of ways, and if nothing else, different.