I have another thread going where I am asking for advice about dry grinder wheels, but do mention that I also have a Tormek. My experience is that it does a great and very easily repeatable job when sharpening all of my turning tools. Its very difficult to grind away lots of metal and lose the shape of the tool. If you have really short tools, the standard turner's jigs will not work very well - I'm talking about the little PSI 1/2" oval skew that I "learned" sharpening on with a dry grinder. It works for all other 'normal' sized tools.
Now with the above said, I have used a combination of the Tormek and dry grinding methods. I love using the Tormek for my oval skews, standard skew, all flat blades (chisels), and my spindle gouges. I also use it for a couple of my bowl gouges - I started sharpening them on the Tormek and keep the grind settings. I have moved towards the dry grinder for a couple of my bowl gouges simple because of speed and convenience. I don't get the same edge, and I don't think its lasts as long, but I don't think its needed for rough work. I also use the dry grinder for my scrapers and parting tools - again, easier tools top sharpen and speed. When I use these latter tools I tend to sharpen quite often. I do like the honing wheels on the Tormek in between sharpening.
One other thing - As far as messes and health hazards go, the Tormek wins hands down. There is very little water than splashes around, and some honing compound that makes its way onto the bench. When dry grinding, there are sparks everywhere in a 'wood shop' and when truing the stones you get fine nasty dust flying everywhere.
It is a great, but pricey tool.