I normally stay at Starwoods, but it is not always possible, depending on where I travel.
I have had the SPG Amex for several years and I think the it is great. However, about 3 months ago I called Amex and asked them to switch my card to a Surpass card. During that time, my spend was over $40k and I am now a Hilton Diamond until 2011. I also received all the bonus points promised.
Last week I called Amex and asked them to switch me back to the Amex SPG. That card arrived two days ago and now I am back earning points in the SPG program. So now I have the best of both worlds
Jeff