I have had hits and misses with Suite 701 every time I have been there. I have gone for dinner there and for just drinks. Sometimes the service has been good, other times they were clueless (for example almost losing my credit card).
The food is quite good. There are also a lot of choices for what type of drinks. The DJ spins some good tunes late at night, but the last time I was there the place was half empty.
The rooftop is pretty cool because Montreal is sorely lacking in the rooftop terrasse department. Definitely check it out on a warm summer evening.
I would recommend Suite 701 to start off a night of boozing in the Old Port.