I've traveled to Pittsburgh on business about 6 times and all but once I stayed at the Pittsburgh Airport Marriott. It's super close to the airport so it was a great location for my work, but if you are visiting the city and want to sightsee, it can be a bit out of the way. Yet, with free parking, and being not far off the highway, I would recommend it anytime. :-)
Rooms: Lovely hotel, standard Marriott rooms and quality I've come to expect. When I visit during the week having access to the concierge lounge is always a bonus. Always clean.
Staff: Never an issue. Quick check in. As a matter of fact, the last couple of visits staff recognized me and called me by name as I entered. Rooms keys ready to go and room prepped exactly the way I like. Housekeeping is very pleasant and quick to respond when I need extra towels or something to that effect.
There is a in house restaurant with a pretty decent happy hour - though I've never partaken. I've had plenty of room service from the restaurant so, I am guessing the quality of food (good to great) is the same downstairs as up in my room. Breakfast in bed was amazing and always prepared perfectly even when I make special requests.
Fitness: 3 to 4 stars for the fitness facility. I think thy remodeled it just before my last visit, but I didn't have a chance to visit that trip.