Huge fan of KEF here - when I got my first "real" HT setup in 2005, I auditioned KEF Q series speakers against a variety of other brands at a similar technical spec, and I preferred the sound of the KEF speakers to all of them, some of which (like B&W) were nearly twice the price of the KEFs.
For me, the thing that sets the KEF speakers apart from their competitors is the UNI-Q array, which puts the tweeter directly on top of the midrange cone, rather than above it. As a result, the sound emanates from a single point, and the clarity is remarkable. The Q series speakers have a frequency response that goes up to (I think) 28kHz, whereas most of the competitors in their price range only extend to 20 or 22kHz at the most. I think their next line up, the R series, extend upwards of 50kHz.
KEFs also had (by far) the widest dispersion angle of any speakers I listened to, which for me was a massive benefit for multichannel music listening - with cheaper speakers, it seems like the sound radiates out of them in a laser-thin column, and if you aren't sitting exactly in a position equidistant from all of them you miss out on half of the sound. With my KEF setup, I could have friends over to audition surround music and I didn't have to have them sit on a chair in the middle of the room - sitting on the couch on the side of the room, or in the armchair at the back was nearly as much of a "sweet spot" as the actual mathematical sweet spot in the middle of the room. I had several "civilian" (ie non-audiophile/non-surround) friends over to hear my system, and not only did every one of them rave about the experience, at least 3 of them that I can recall went out and got surround systems after hearing mine.
I still covet KEF speakers to this day, to the point that even though I can't afford them right now, I still semi-regularly visit their website and gaze lovingly at the various models like a little boy with his nose pushed up against the glass of the toy store front window.
