FFW is a good, cheap and easy way of getting 36 engagement points, but still being able to ride with gears.
I have had no major problems with running an ACS Claws freewheel on my Tensile cranks, but fixed hubs are still something that needs taking care of by the big companies. Echo and Try-All hubs are expensive, and cheese, especially the ones of Echo variety, or so I have been told.
I ran a locked out Deore hub for about 10 months. The only downsides are that it's heavy, needs constant tightening, doesn't spin very smoothly and the axles eventually snap. Spare axles are readily avaliable for a fiver from most shops though.
All in all, a great way of trying quicker engagement for not that much cash, if you have a set of threaded cranks like Echo, Tensile or Try-All that is.
I'm going King now though. Gotten fed up with the Deore hub on the back, and want to see how I get along with double the engagement.
ACS are hugely underrated items though. Keep it tight and clean and you'll be laughing.