I've used the Spyderco ceramic stones for a period of several years. Like every other method of honing, they have their advantages and disadvantages.
The first sharpening method I used was a Norton India combination stone, in a wooden box. It worked fine to put edges on tools, but in my ignorance I didn't seal the box with varnish or similar, so it soaked up oil from the stone, and started contaminating everything it touched. So I put it aside, and tried waterstones, which were very fashionable at the time. These worked fine too, but in the limited space I had to work in, the mess was a major problem - they are not bench-friendly.
And so I came to look at other ways to get an edge. I bought a ceramic stone (the medium) and found that it was not only bench-friendly, it was very compact to store. It gave a fair edge (comparable to or slightly better than the India), though it was not as fast-cutting as the India. I later invested in (using the word 'invested' deliberately - these things are damned expensive in the UK) an ultra-fine, which cuts very slowly but gives an excellent edge.
However, I found that neither stone likes being used dry - both my medium and extra-fine tended to glaze with ground-in metal, and cleaning them needed quite aggressive scrubbing. I took to using them with water having a little drop of washing-up liquid in it to kill the surface tension, and have never subsequently had to clean them.
The oft-reported problem that the medium stone is not flat is true, though mine was out of flat by only about 0.25mm over it's full surface, so I used it as it was; I wasn't going to shell out for a very expensive diamond stone just for the one job of flattening it. Despite not being absolutely flat, it did a perfectly acceptable job. The ultra-fine stone had one face ground flat, and apart from some residual grinding marks, it was as near perfect as one needs.
More recently, I've gone back to using the fine India, paired with a Dragon's Tongue Slate. The India cuts faster than the medium ceramic, and (whilst this is a subjective judgement) the Dragon's Tongue gives a slightly sharper edge than the ultra-fine ceramic. I'm not sure why this is, since the 'numbers' suggest they should be about the same, but the nonetheless the sharpest edges I've ever produced have been from the Dragon's Tongue. That, however, is on the simpler steels; I don't have any of the modern everlasting wonder-steels.
So, in summary; The ceramic stones are very compact to store and easy to use, but do benefit from use with something to float off the swarf. They are expensive in first cost (the ultra-fine cost be just shy of £100 - the Dragon's Tongue was less than £15 delivered for two). The medium is not absolutely flat (it's 'flat enough'), and is slower cutting than a fine India oilstone, though gives a slightly more refined edge. The ultra-fine is flat enough to satisfy all but the most pernickety, and gives a pretty good edge, but not quite as good as a Welsh slate. Both oil and ceramic stones are easy to use at the bench.
Would I recommend ceramic stones? On balance, if you're prepared to swallow the first cost (which in the UK at least is quite high), they should give a lifetime's good service, and do a very acceptable job. They are not perfect (no system is), but they are a very viable option.
This is most emphatically NOT an attempt to have a go at anybody, or fan any flame-wars. It's just my experience and honest opinion, posted with the intention of adding a little to the sum of human knowledge, and in the hope that it may inform others a bit. If anybody wants to pick a fight with me over it - shove off, I'm not interested.
Nothing like a good sharpening thread to get the pulse going - better than aerobics? 
