Doesn't have as much camp and humor as the original Ghostbusters movie, but is a more than compelling mystery involving an excellent cast of both youth and experienced actors. Add in some cool CGI effects and some awesome (more than) cameos and this movie has everything a sequel of a beloved original should have.
What it lacks with a living Harold Ramis, it makes up with heart and dedication. Definitely go see this one if you loved the original and keep an open mind. It's really, really good.