Our "suite" (tiny by American standards) overlooked gorgeous Green Park. The hotel was beautiful and clean, the service was excellent, and there were many luxury amenities. However, other than sleeping and showering, we spent hardly any time in our hotel.
The hotel is very conveniently located in the heart of the city. Park Lane is also close to a Starbucks, which is great for a quick breakfast, and to the TUBE. We were able to get everywhere from the Tube stop, and walking around Mayfair was lovely. If you have plenty of time, long walks can take you all the way to Trafalgar Square, Whitehall, Westminister Abbey, and the Parliament Buildings. I would definitely stay there again.