There are a couple of extensive threads here devoted to the whole home-grown points vs. air-miles vs. rebate card discussion. Try a search on "home-grown" (or try one of the home-grown programs like GoMiles, WorldPoints, etc.).

My conclusion is that although I think I would be a perfect candidate (based on my spending/travel) for a home-grown points card, none of them are what they appear to be. They contain vague T&C's, half-baked websites, poorly-supported processes and procedures, and tend to change at the whim of the card issuer. The changes are never in the favor of the cardholder.

Until a home-grown program comes along and gains enough critical mass to warrant quality processes and support, I won't consider these types of programs. It's too risky to tie up 20,000 or 30,000 points only to find out that I can't get a ticket. I'd rather just have my 30,000 Starpoints and go stay in a nice hotel, even if I have to buy the plane ticket.

(I guess you could consider Diner's Club a "home-grown points" program. If so, then they are an exception - it's a pretty good program that is a hybrid between a mileage card and a points card. They have a critical mass of members and probably won't go away overnight. They have only devalued their points-to-miles conversions once in the past few years, and it was only a mild devaluation.)