I have three portable bluetooth keyboards.
Microsoft Wedge - A competent keyboard. There's a newer version that lets you switch between multiple devices. Unfortunately, I find it too small for extended use.
HP K4000 - Being only slightly bigger than the Wedge, it does offer a superior typing experience, though lacking the nice keyboard cover that comes with the Wedge.
Logitech K480 - The biggest of the three. Size makes it the easiest to type on. It also has the ability to switch between multiple devices.
However, overall, I wouldn't call any one of them a knock out of the park. My nod goes to HP K4000 for being easier to type on than the Wedge while also more portable than the K480, but perhaps others have better suggestions.