Someone recently asked us what the heck it is we do all day at the Cars.com offices, you know, besides blogging here on KickingTires. Well, one of the things we do is compare some of the big players in segments from convertibles to SUVs. This month we took three of the best entries in the luxury sedan market and compared the good, the bad and the kind of expensive. The 2008 BMW 528i, 2008 Cadillac STS and Infiniti M35 deliver style and value, but which one brings home the win?