Running Pilot A/S plus for about 11k miles now and still have plenty of tread to go. These ride way nicer than the stock RFT - softer, grippier, and quieter. I kinda like the tread design too.
Excellent rain and wet traction. Even had decent snow traction this winter in Colorado.
I really don't think you will notice a performance reduction unless you track your car. I drive the mountain roads spiritedly and am always impressed with the handling and ride.
I have cashed in on certificates in the past. I really think they are a good investment, but that's just been my luck with tires... Any thing like that is a gamble. I also carry a BMW flat repair kit since I ditched the RFTs and don't have a spare.