Pros and cons of mechanical vs hydraulic disc brakes?

Feeling somewhat unsatisfied with the V-brake setup on my cyclocross
forks I'm contemplating disc brakes as a solution and am wondering
what the relative merits of hydraulic vs mechanical are?

So far I can think that the mechanical variety are probably cheaper
and easier to fix/adjust at the road-side whereas the hydraulic sort
have more bling and stopping power (maybe - don't know why?)

Also, any recommendations for a 100mm front fork with ISO disc tabs?
So far I've found Winwood and Airborne Aeileron - but both are US
based and don't seem to any stockists in the UK

http://www.jensonusa.com/store/produ...ross+Fork.aspx
http://www.fixedgeargallery.com/2006/nov/JasonElias.htm

Many thanks,

Duncan.