Mabi is an old converted cinema, but you would never know it. The hotel is a very modern, small (boutique) hotel with a great price-tag. The front desk staff were extremely helpful. The rooms were well appointed, with free wi-fi, very nice bathroom amenities. The beds appeared soft (an initial concern) but we slept very well, so our concerns were unfounded. There was no extraneous noise from outside, although we did not stay over a weekend.
Special touches include: a tray of apples in the lobby for guests to munch. If you prefer, there are jars of sweets. There is a small library from which you can take reading material if you forgot to bring your own. And best of all, every night from 5:30 to 7:00PM there is a free wine-and-olive tasting. And finally, a small cinema that screens films every night (new ones each Friday).
We did not try the breakfast, so I can't comment on that.
I would highly recommend this hotel to all Maastricht visitors. It is very conveniently located (near the market square, and about 200 meters from bus stops).