So Close To Fine
My wife and I stayed at the Marriott Waterfront while attending a large conference there. The hotel was busy as a result so just a few comments on what might stand out to other visitors.
While our room rate was acceptable, Marriott's policy of charging $13/day for slow wireless internet is past its sell-by date. There's free wifi in the lobby, which rubs in the mispricing. 
We had a nice light lunch special in the 700 Grille (soup, 1/2 sandwich and small salad for $15) but didn't return because of the disjointed service from distracted, listless (and frankly unkempt) waitresses. 
In our room we could not figure out the long reach over the granite counter to a tiny sink. Odd. The Direct TV system is slow, pesky to use and not as good as you have at home, but how many hotels are similar. Fortunately, our A/C warded off the blistering heat if we didn't open the drapes.
Now the better:
Desk and lobby staff were friendly, responsive and efficient. Check in went flawlessly. The doormen gave good directions to local restaurants but probably could have fewer buddies hanging around.
The bar, Kozmo's Lounge, was excellent. Although the drinks are expensive, the room is overseen by charming, adult women who gracefully look after patrons. The mix of seating offers good options for pairs or small groups and the bar staff are friendly. 
There's a water taxi dock right outside, offering a good way across the inner harbor to Fell's Point, Fort McHenry, museums, aquarium, shopping, etc.
It wasn't what you'd call a bad stay at the Marriott; we were focused on the conference - which may have made the difference in their rhythm. We felt sorry for the management (and our organizers) when the escalators leading to the main conference area broke down on day one, creating long queues at the lifts throughout our stay. 
There are plenty of options in Baltimore; it's a great place to visit. When we're next in town we'll probably stop into the Marriott Waterside for a drink.