If you asked me this question pre-200, I would have said, "A great mid-range, followed by good imaging, a high-end that's not shrill, and a bass that's responsive and un-muffled". Of course, with my price budget, I could never get everything I wanted in a speaker. Now, with sub-woofers really coming into their own, having a set of mains with really good bass isn't nearly as important. With a good sub, all I need is a speaker with good high to mid-range sound and corresponding imaging (with some forgiving speaker placement- if it's not too much to ask). All these qualities, I believe, are now within reach of a lot more people.
With that said, I would also like to add to my list anything but a black finish!