The exterior of the property is stunning, as is the lobby. The Chambers Lounge, which is only available to Marriott Platinum members (not Gold), or guests staying in the Chambers section of the hotel are allowed in. The property is really 2 different hotels, the Barlow and Chambers. The Chambers section is what you see in all of the pictures. The Barlow section, where I have stayed on my 2 visits here, is pretty average, as far as Marriott's go. That's to say it's a nice place, but there's really not anything unique to it. My room this time did not have a tub, while the room on my last stay had one of those nice, deep European style bathtubs. Marriott Platinum members are not upgraded between the Barlow and Chambers rooms. Staff were all pleasant, but did not seem particularly warm (though this has been my experience more or less in every hotel in London in 15 trips over the past 4 or 5 years.) Room size in a Barlow King is decent. Breakfast in the Chambers Club is excellent.
The location is awful relative to where I work (oh what we will do for points/status), but it is nice to be attached to the St. Pancras train station with all of its amenities. Highly recommended if you have an early Eurostar train to catch. This isn't in the touristy heart of London, but if you are ok with a Tube ride, there are tons of tube lines running through the station.