I'm the only person that I know who runs a front freewheel on a stock- and one of only a few on here.
I bought my trials eno from "jimbo" for £65ish and have had it for over a year. NO problems with it (never skips), and i have taken in apart only twice-once was to grind the tabs off so give me more clearance against my BB (and the freewheel still works!)
I'd really recommend them to anyone- the price may sound steep but the quality and durability are first rate.
adam