I stayed at St Gerlach for 4 days for a business conference In March 2012. The hotel is impressive to look at, has nice gardens and a nice spa / pool area. I ate breakfast and lunch here, which were alright (standard-fare for a hotel) although I didn't eat an evening meal here so can't comment.
The staff are friendly and helpful.
I was staying in a two level apartment style room which was pleasant enough although I found it a little cold (in the aesthetic sense of the word). The bathroom was huge - as big as the room easily!
Maastricht isn't the most exciting of towns in terms of nightlife but is located a reasonable distance from some bars and restaurants. Impressive since the pictures on the website give the impression that it's in the middle of nowhere!
No real complaints about the hotel other than that the wireless service is terrible. The signal comes and goes. Probably due to the sheer size of the hotel. They just need to add some additional routers for the rooms in the buildings further out.
Probably a good place to come to for a romantic getaway or if you're looking for a different side of the Netherlands.