For whatever reason, Boston hotels seem very tight right now--I had two trips planned and had a lot of trouble finding anything decent at reasonable rates, including on PL, Expedia, Quikbook, etc. One other possibility if you're not going to need to go back and forth to the room all day would be to try Priceline for the airport zone (the trip inbound on the T is quite quick and cheap enough at $1.25); when they have inventory, the 4-stars there can generally be had for $50. The Hyatt is very nice; I haven't stayed at the Hilton.