When I got my Cambridge Audio electronics (Azur 340C CD player and 340A integrated amp), I was impressed enough with the performance/price that I had to try their speakers. The $260/pr S30s are the only speakers they make, and they recommend them with all their electronics (some of which are way expensive). That should tell you something right there.
The S30s are really small even by minimonitor standards. The size is mis-stated on some sites, but is actually 9" high X 9" deep X 6 1/2" wide. Given this (and their rating "on paper" of 55Hz), it would be easy to think that they would be bass shy. In fact, they passed every bass challenge I threw at them (from Brian Bromberg's acoustic solos to Bill Lasswell's dub) with flying colors, not only with every note present but with vanishingly low distortion and often tactile impact.
The excellent imaging that minimonitors are known for is present in spades (perhaps not the largest 3-dimensional a soundstage around, but laser-etched precision), and the overall sound is super clean and detailed. As with the bass, high-level dynamics are also surprisingly strong, easily holding their own against small floorstanders such as my Mirage Omni 350s. They also passed my harmonic distortion torture test (Javanese gamelan orchestra) without breaking a sweat.
Most impressive of all is the complete lack of the "boxy" quality that I associate with small speakers. In fact, they are highly transparent and often not identifiable as the source at all.
To say merely that I am impressed with the S30s (and the Cambridge system as a whole) would be an understatement. I am not certain yet that they will displace the Omnis as my long-term favorites, but given that those are 4 times the size and 2 1/2 times the price, the mere fact that they might displace them is amazing.
I have heard a lot of minimonitors and small bookshelves that cannot compete with the S30s, including some a lot more expensive (eg the $1000/pr B&W CM1s.) I agree with What HiFi that the system as a whole is the one to beat at the price (just under $1000 total.)
Both the speakers and the Cambridge Azur electronics receive my highest recommendation.