Excellent Location, Good Amenities
I chose to stay at the Boston Park Plaza Hotel & Towers for one night due to it's location (and a deal I found on a website). It is located one block away from the Boston Common & Public Gardens, 2 blocks from Emerson College and one block from the beginning of Newbury & Boylston Streets (ie, walking distance to Copley Square, Prudential Center, etc). It is also close to the T (subway), one block away from the Arlington stop.
The hotel lobby is nicely furnished and looks swanky. Reception was efficient and we received vouchers for a continental breakfast (which we didn't end up using). While the lobby is attractive and upscale, the hotel itself appears a bit old. This is probably because the hotel IS old (1920s!) The floor hallways are redone and are clean, no odd smells. The rooms themselves are on the smaller side; our room had a tiny bathroom (think: door swinging right past toilet, pedestal sink right next to the shower). The bathroom fixtures were updated for the most part, so the only downside was not being able to manuever around or have a lot of room to put toiletries.
The bed in the room was very comfortable; there was a flat-screen tv, black-out shades and a pod coffee machine. 
All in all, it was a good stay. I would choose this hotel if visiting Boston for the first time and intending to be walking around, visiting sites, etc.