I recently took the plunge, and replaced the crap stock Toyos with 215/50/17 Continental Extreme Contact DWS's, which got great reviews on Tire Rack's website. I only have a few hundred miles of nice, dry weather driving on them, so I really can't add my own $.02 yet, except to say that they're comfortable and quiet.
I also really liked the Michelin Pilot Exalto A/S that I had on my old 5. They were great in the dry and wet, and got us through 3 NJ winters without much trouble. I was contemplating getting them again, but the Contis were cheaper, W-rated (vs. H-rated for the Pilots) and had great ratings for wet traction.
I'll post a better review of the Contis after I put some more miles on them -- especially in wet conditions.