My group finished playing this tonight. Took us 2 sessions. We used a system called Dark Streets and Darker Secrets, which worked very well. We had a lot of fun and I'd totally recommend this adventure!
The adventure can go a number of different directions, depending on what choices the players make. I think it will have great replay value.
I would recommend playing it as a one-shot (as we did). It may be quite difficult to get all the PCs out alive from this scenario (3/4 of our PCs died in the end).