I know you guys are talking about weathertech mats and GM all season mats. Though not the brand name of weathertech and not 100% the exact design for the Regal of the GM mats, I picked up a set of all season rubber floor mats from Sam's Club for $20. This included 4 mats, 2 for the front driver and passenger and 2 smaller ones for the rear. The fit pretty well actually for being a generic mat. They have pretty deep wells so dirt and grime sets in and isn't sitting on the top and it also has a decently deep trim around the edge to prevent anything that gets on the mat to spill through onto the carpet. Since it's a generic mat, it has some excess material around the edges. This can be trimmed with a pair of scissors for better fit in the Regal - that's what I did. URL for what I purchased: http://www.samsclub.com/sams/shop/product.jsp?productId=prod4170012&navAction=push
Worked really well through my Michigan winter and I plan to keep them for a while. Though not as nice as Weathertech products, it was a cost effective alternative for me at just $20.
I'll be going with the WeatherTech floor liners. Had them in my TrailBlazer and put them in my mother's Rav4 and couldn't be happier with them. They are always a perfect fit and the design keeps anything from getting to the carpets.