We stayed here one night before flying early out of London and found it to be very posh and comfortable. Lots of nice subtle touches, and it's connected to Heathrow Terminal 5 for convenience. I definitely wouldn't stay here for sightseeing in London since it's almost an hour commute to the city from Heathrow.
Comfy beds! Great showers! We were able to get connecting rooms for our family, plus got a free room upgrade.
The only thing we didn't like: there was no natural daylight, as the windows in our rooms looked out onto an interior atrium.