If you don't have plans to see this movie, you can check the spoilers here and then come back.
This is not a "good" movie in the sense that the pacing is funky, the dialogue is often crap and the 3-D is completely tacked on; a film student would probably have a heart attack after watching this. Is that of any relevance as far as its entertainment value? Not as far as I'm concerned. I had a helluva lot of fun watching this, and not just in a "so bad it's good" way. Here's an instance where clearly the director and particularly the actors saw they had a pretty hokey script--perhaps intentionally so--and rather than try to make it anything but that, just went to town and had fun. Watching Colin Farrell was a delight; the same as when he played Bullseye in Daredevil, as the vampire Jerry he just enjoys the heck out of not just every line he delivers, but every millisecond he has to mug for the camera with a twitch or smile or goofy face. Farrell knows the perfect line between campy and cool and it's a joy to watch the man work. While he can't touch Farrell--nobody could have--David Tennant is pretty great in his own right as a Criss Angel parody with a dumb secret origin that, again, works because they don't take it too seriously. Christopher Mintz-Plasse plays the same character he always plays and has limited screen time, but if it ain't broke, don't fix it. Anton Yelchin has the unenviable task of being the comparably square hero between the twin towers of Farrell and Tennant, but he brings some to the role, and even goes for a little pathos on occasion. I'm not sure exactly what Fright Night was meant to be, a full-on horror comedy or a traditional horror movie; it wasn't that scary, but it was hilarious and fun, so I hope the goal was the former. It has slow moments, there are some points where the plot is too bad to even laugh at and, again, the 3-D was absurdly gratuitous, so I can't give it quite top marks, but for the most part it was pretty enjoyable and even occasionally clever, so I tend toward thumbs up. If you're expecting the next great horror movie, skip this, but if you want a fun diversion under two hours, I think you'll be pleased with this.