What I want to know is - is the range good? Is it efficient? Is the gap between the gears small enough so I have choice? Is it reliable? Is it really maintenance free?
I find the range great and use all the gears from 1-14. I do spin out on 14 going downhill and I might add a few teeth to the chainring to up the gearing slightly.
Efficiency is comparable to a derailleur system, better in some gears eg direct drive 11, worse in others eg. 1-3, but it doesn't deteriorate when caked in mud. See here for data and a discussion:
http://www.ihpva.org/HParchive/PDF/hp55/hp55p11-15.pdf
Maintenance free? Mine's done 6k miles. I've changed the oil twice and wipe the chain down once a month. I tighten the eccentric every 6 months or so. I've also reversed the rear sprocket. It's used every day. I will change the cables at 10k miles.
It depends what kind of riding you do. I need a bomb-proof load-carrying commuter and something I can use to tour on. I ride a lot of offroad tracks and hate digging crud out of derailleurs. I have worn out a lot of bikes and wanted something that will take this kind of use for 10 years or more. If you only ride on roads, are happy to keep your drive chain as clean as Mick's(!) and want a traditional British tourer then there are possibly better and certainly cheaper options. I've no regrets and wouldn't go back to derailleurs.