Online Travel Booking and Bidding Agencies - Any experience with FlyL4L or similar mileage broker

Does anyone have any experience with mileage brokers? I found this outfit Flyl4l (luxury for less) online - their business model is apparently to buy up corporate air miles at a discount, and use them to redeem flight on your behalf. It's the first I heard of anyone doing this - but the quoted price was about 60% of the web price for a virgin upper class seat to capetown.. only a few days adrift of my preferred dates.

I'd appreciate anyones thoughts/experiences with this or any similar company - apologies if there are threads on this subject I searched for FlyL4L and nothing came up.

Thanks

Hugo