Agreed - the Skyline is a good hotel. The SPG Platinum amenity is normally a bottle of red wine and a big plate of chocolates!
On the other hand, it is often fully booked - yes I can get guaranteed room as Platinum, but at rack rate, which is quite a lot of money.
It's also a pain that the shuttle bus to Terminal 4 doesn't run any more (this is not really under the hotel's control I guess) so the choice is a taxi ride costing 10 quid or the GBP2-50 shuttle bus to T1 and the (free)
Heathrow Express train to T4, which means a very early start if you have a morning flight.
And the phone charges are absolutely outrageous (as they are at all Sheratons and most other hotels in the UK).