I am presently putting up a new sheetrock wall in my kitchen & am wondering
what is the easiest correct way to handle the joint where the (popcorn
painted) ceiling meets the new wall? (Taping the corners is no problems as I
can just fold the tape in half, apply it to the corner & then "mud" it)
Where the ceiling is textured however, is there a way to tape the joint
first (without having to manually sand off the pebbling) or should I just
apply joint compound to the seem as best as I can?

As you were messing around the area where the new drywall butts up to
the old ceiling, does the acoustical texturing want to come off easily?
If so, remove enough to tape and mud, then re-texture the new ceiling
blending the new texturing on to the existing.

Alternatively, you could remove all the acoustical texturing,
re-texture the whole ceiling. DAGS in the news groups, lots of
information on removing texturing...

Good luck...
Darwin