Twice.com has an interesting article about the 2006 Cobra and Whistler detectors [free registration required].
They point out that the new Cobra models will support the Ku band, but the Whistler's will not. Whistler's research apparently determined that the Ku band will not be used in the United States in the "near future".
New from Whistler are a couple of detectors with remote controls. They are also following Bel's lead by offering models with exchangeable colored trim.
From the article:
Whistler's new 2006 detectors include two with remote control modules and several models with exchangeable colored trim plates. The XTR-220 and XTR-520 come with a remote control that is useful in SUVs or minivans that have large windshields or dashboards where the detector may be hard to reach.
Whistler also has a model that will let you totally customize the detector's alerts. You can record your own audio message to play, and even customize the display text for each alert. I'm sure the enthusiasts could have some fun with that feature!
UPDATE 2/6/06 - The article is incorrect. Some Whistler XTR series models WILL support the Ku band.