The last, and stickyest part about a transitioning pilot
is the flight review requirement.

Does a pilot transitioning from gliders to power (or
vice versa) need a current flight review to fly solo in
the new category?

Kind of awkward to require a customer to go get a
flight review in a different cat and class (which he's rated)
before you can solo him. This doesn't make common sense,
but if you don't believe he's a student pilot
then he needs a flight review to fly solo/PIC, since
61.56(g) does not exempt him from the requirement.

But hmmm...I don't see any requirement that a pilot
fly in an aircraft in which rated in the Wings program
rules...
http://www.dayafss.jccbi.gov/ac61-91.htm
So perhaps one can do a flight review this way...