Here is some stuff I put in another forum about mine, a Dynamic/Newport :
"Here's from someone who owns one.......
The shaft will never wear out if its greased. Its sooooo overbuilt.
I cant see it ever needing to be replaced, despite what the guy at Dynamic
sez. Show me someone with 10K on one to disagree and Ill believe otherwise.
The problem I have is with the bottom bracket that is underbuilt. That is
the weak link on my Dynamic/Newport. It requires constant tightening of
all of its three, whoppingly huge, 2.5 mm screws. There should be at least
two more and of a larger diameter. If you've ever had your new bike sand blasted
on the coast of Florida, or tried to ride year 'round in Vermont and want gears
or need to carry your bike up a flight of stairs and not enjoy grease on your clothes,
you will understand why some people like them. If you want to make time with
the local Carbon Fibre, Power Ranger clubbies, it isnt the bike for you "
As far as efficiency, You can feel a slight difference between the chain ad
the shaft but I always can keep a constant 20mph with no problem.
This is FL, though