We started this design over two years ago using fluid css grids. When we started to test some older, crappy browsers (specifically IE6 and IE7), it became nearly impossible to make things work without using tables. But now, 2 years on, we have technically dropped IE6 and IE7 support but we still kept the table structure. I don't think it'd be too hard to go back to not using tables, so maybe in the near future. And of course, I would also really prefer not to use tables in the layout :), but it had to be done back then.