I second the vote for Starwood.

Here is the way I look at it. Most frequent flyer mileage addicts like myself are trying to collect points and miles for use on vacations. That being the case, one should consider that much more time will be spent in and around the hotel room during a vacation versus the time spent on a flight. Besides, there is usually a good deal to be had on airline tickets regardless of the season. However, good deals on a first rate hotel during high season is a lot harder to come by.

Among the major hotel chains, Starwood is by far the best in terms of availability, points required for free nights, number of properties, and ease to become elite members. With the latest acquisition of Le Meridian (hopefully will be integrated into SPG), Starwood is no doubt the best value out there.