Ghostbusters is pretty damn fun so far. Initially I had some issues with dodging enemies' attacks (WTF is up with the onslaught of bellhop ghosts in the hotel lobby coming BEHIND you and attacking without warning?), but got used to it by the end of the hotel level.
The game is essentially a third person shooter, but the twist is that any of the spirt-like ghosts need to be trapped, so you're essentially using your proton beam to grab, slam, and drag the ghost into a trap area. It's done well and makes the game a lot of fun; had they screwed up this mechanic, the game would have been a mess. The game is basically parts with you walking around investigating (you can use your PKE meter to scan for hidden ghost spots and also bust up shit for extra cash), and then ghost encounters against both corporeal and ethereal forms. The physical manifestations you destroy, the spirit types you trap. Haven't gotten to use the slime stuff yet, so there's more to come. Dodging is done by hitting B, and you can also hold down B to do a Gears Of War style roadie run. When your CPU-controlled teammates fall, you can also revive them Gears style. I also like that you can do the roadie run when in PKE scanning mode and that the PKE meter will come right back up once you let go of B.
And yes, the game is positively oozing with Ghostbusters fan service. Any fan of Ghostbusters is sure to enjoy the hell out of the game; yes it's definitely a game "for the fans," but that's because even the play mechanics are taken right out of the way the things happened in the movies. The game plays great, the dialogue is fun, and the atmosphere is very well done, both in bringing the movie to life with the visuals and familiar settings/music and in making things creepy when investigating. They do a good job throwing things at you and you don't know what's coming next. Good enemy variety too. Depending on how fun the online is, I'm thinking this is going to end up a solid B title, taking off for its apparently-short single player game. Definitely worth a rental for fans and a purchase if you're a huge Ghostbusters fan.
Oh, and installed load times are around 20 seconds (maybe less?) or so. All of the loading screens also have cinematics playing, so it's a very smooth transition. When you load up a game or restart a checkpoint, it plays a video with tips on how to play and the Ghostbusters theme. It doesn't feel tedious and incredibly long because of this, unlike say, Bionic Commando.