Ian,
I can only address your first question, having used the TM Sprint and
then following it up with a Modena before making the jump to pedals
just last year (and to force feedback just last week).
In terms of build quality, I found the Modena to be much better than
the Sprint. The wheel rotated smoothly, and it was nice not having to
deal with potentiometers. Also, the wheel is almost dimensionally
identical to the Sprint's (but angled slightly back) and rotates the
same 180 degrees. And, yes, the wheel supports separate axes for gas
and brake.
However, some things took some getting used to. The button placement
is awful. While I appreciated the two four-way hat switches on the
wheel, the only other two buttons on the face of the wheel are tiny
and located low and in the middle of the hub. Hitting these buttons
while working the paddles and turning the wheel was not easy. The
paddle design is also inferior to the Sprint's. First, you only get
to use the lower half of a paddle as an axis; the upper half counts as
a button (presumably to be used for shifting). The paddles also have
a small amount of travel. This was probably the hardest feature to
get used to, especially in throttle/brake-sensitive games like GPL.
Finally, the pedals -should you decide to use them- are below-average
(though not nearly as crappy as that lump of plastic that came with
the Sprint).
I ended up mapping the shift functions on the shift levers and on the
buttons in front. That way, I'd have at least one button I could
reach regardless of the position of the wheel and which paddle I was
working. The paddle travel issue I learned to live with.
Hope this helps.
Martin