Re: jackshift worth it?
Yes that motor will wrk fine with the shiftkit. I don't know what your background is mechanically but the shiftkit is not the bset thing if it is your first build with a pretty good mechnical background. Also it is not the engine you have to worry about the shift kit fitting it is if the shift kit will fit you bike with motor in it.
Now that that is out of the way. the anser to your other question is yes it works awesome for hilly areas cause you can keep the motor in the sweet spot rpm range when going up hills. If you have time use the search feat and there are plenty of post and threads that go into detail a little more for you.
Work hard, Play harder and enjoy the Ride!!!!