Regarding the comments made on the K750, I think it sounds a pretty cool piece of hardware - it does cost more, yes, but you do save on the batteries long term. And the keys are supposedly nice to type on, except for some sizing problems with the 'Enter' key (which this review points out).

Though I guess the feel of keys is subjective, of course, as someone else pointed out. Well worth thinking about, anyway - and quiet to type on, too, which is always nice...