I've just returned from New Year spent at the Marriot West India Quay.
We had a room in the "tower", as opposed to the nasty looking block at the back. We were on the 7th floor (same as exec lounge). The room was located at the front of the hotel and had an excellent view through floor-to-ceiling windows of the Canada One tower, the other towers and the City (towards the gherkin).
The room was very nice indeed - the usual Marriott generic room - but nevertheless very comfortable and new.
As a gold MR member we had access to the exec lounge, which re-opened following christmas on 31 Dec 12 noon. The lounge is on the 7th floor and is located in the corner of the hotel and afforded the same spectacular views as our room. During the day hot and cold drinks were available with just crisps and a few chocolate bars. Between 5 and 7pm hors d'oeuvre were available, 7 to 9pm was desserts, these were pretty good. The best thing, for me, was between 5 and 9pm wine and beer was complimentary. So to my mind, this easily beats my only other experience of an exec lounge in the UK, namely Chancery Court.
Breakfast was the usual cold continental stuff, but additionally hot scrambled eggs and bacon (albeit crispy "American style") were available.
I would thoroughly recommend this hotel, and would suggest you ask to be located in the tower, preferably on the front, preferably on a high floor. Given that the cost of the room was £72 + VAT a night (booked on the M11 code) is about half that of most other Marriott hotels in London it is fantastic value, and a very nice location to visit the bars around Canary Wharf.