My family and I stayed in this hotel for 4 nights in the 3rd week of December 2007.
When we checked in, they showed us a tiny suite for 4... my dad felt suffocated on entering the suite and when I called the reception, they immediately arranged for us to be shifted to a palatial suite... at no extra cost. It was so speedy and done with so much courtesy that I was really astounded and happy.
The service, throughout our stay, was like this... prompt and polite, and no one lingered for a tip. Rooms were cleaned and made up everyday, it was spotless. Sure the corridors smell of smoke, but what do you expect from a smoking floor?
The revolving restaurant in the top had some amazing views and will be ideal if you have someone with you to impress. Yes, the food is overpriced, but the ambience makes up for it. The complimentary morning buffet (served from 6:00 to 10:00) is delicious and had over 30 dishes, even Indian pulao!
There are, however, three minor problems I had. The pool was open only after 9am... it was difficult to have a dip when we had a busy touring schedule ahead of us. Like most other hotels in Bangkok, we had problems with English-speaking staff... we had to speak real slow to make them understand what we were asking... and the internet cost 200 baht an hour! Really steep!
Apart from those few minus points, GCP is a gem of a place to stay in Chinatown. The staffs in the reception were always smiling, and the concierge and the porters were very willing to help us, and guide us. I'd definitely return!