strother,
had my 915 rebuilt last year and had the same thing. very "notchy" feeling for the first thousand miles or so. After that it's much more smooth going in/out of all gears. It was a large difference for me too, mainly in that 1st gear would actually engage when I got it back!
but also the gearbox feels more decicive and it's very simple to feel the gear engage. As far as the shift from 1st to 2nd, my best advice is to pull straight back instead of slightly to the left. even with a rebuilt 915, these things are going to require more attention and responsibility in treatment when compared to a modern tranny.