We stayed at Millennium in December over Christmas. I have to give the hotel a mixed review. The furnishings were sophisticated, the beds extremely comfy and the location was grand. In a very expensive city, the value was good.
However, the rooms were small, even the bigger rooms. 2 people could not walk around at the same time. It cost 5 lbs to use the Internet and the closest cafe was at Victoria. My biggest complaint was the concierge and the staff in general. Everyone was impersonal and not particular helpful. So you must balance the value and location with your other needs. In any case you will not go wrong as the feel of the place is very nice and you will sleep well

My wife and I enjoyed a second honeymoon in London over last New Years week. We booked a special thru Go-Today.com and was upgraded to this hotel from the less expensive one we had picked. What great good fortune!

The hotel is tucked away down Sloane street with Gucci, Fendi and Harvey Nichols. Nice neighbors! Harrods is an enjoyable walk around the block. Admittedly, we didn't purchase at any of these places except Harrods (great time of year for bargains there!!), but it was fun to look!

Yes, the rooms are smallish, but cozy and very well appointed. We enjoyed room service several times from the excellent fusian restaurant down stairs. The rate included a continental breakfast which was not served in the main dining room. We did feel a little like we'd been sent to outer Siberia when directed upstairs to this meeting room set up each day for the "tourist trade." But, hey, it was free, so who's to complain? Just be aware of this. Note, there's a very nice automated tea/coffee service on the mezzanine with comfy chairs in which to rest your tired, travel feet during all hours of the day.

The concierge was excellent and secured for us some very hard to get theatre tickets at a decent price. Tube station nearby for running around the city.

All in all, a very nice place to use as your base while touring London.

My wife, 2-year old son and I stayed here for one night. The hotel is beautiful and immaculate. The rooms, as mentioned by several other reviewers, are fairly small but extremely well-maintained, and they are just large enough for basic needs - probably ideal as a business hotel, really.
The only reason I marked this 4 instead of 5 stars is the staff. While not terrible, the front desk staff was fairly aloof, and the concierge did not go out of his way at all to help us find places to go. They answered our questions, but no more.
The Mjo restaurant is superb, and they offer a continental-style buffet breakfast that is second to none: a great selection of fresh fruits, juices, cheeses, cold cuts, several types of cereal, and outstanding coffee.
The hotel is obviously in an ideal location, less than 10 minutes walk from Buckingham Palace, Hyde Park, Piccadilly Circus, and all of the central London sights. Harrod's is just around the corner, as are several other posh shops. The pub across the street, just to correct another review, is a great place to grab a pint, with some superb ambience, but the food is nothing special - I would look elsewhere for lunch or dinner. Chinatown is only 5 minutes by taxi.
All in all, a wonderful hotel in a wonderful location. For cleanliness, location, and accomodation, definitely 5 stars. The service and room size brought it down to 4.

This is a great place to stay if you want class and status. It's comparable to staying at the Four Seasons in Beverly Hills with all the great stores on the same block. And Harrod's is either a block and a half away it you go one way or it's a block if you go down Basil. The restaurants are expensive but there is a real cute pub across the street called the Glouchester which has good food and another cute cafe around the corner off Basil that has good food and breakfast, so it's worth staying there and you can also not spend so much if you don't want to. The staff is very helpful. I plan to go back when I visit again.