I tried it once -- never again. The sweater stank like the kind of cheap perfume people use to try to cover up body odors.
I also didn't like the idea of scrubbing at stains on a delicate wool with the questionable chemicals in the spot remover pads, and not confident that a run through the dryer would remove normal dust and body oils.
I may be wrong about this since I don't still have the box, but doesn't Dryell just promise to "freshen" clothes? That's very different from CLEANING them.
The fact is, any wool garment is easily washable. Superwash wools come through machine washing beautifully, though they're best dried flat. You can hand-wash a non-superwash wool during a couple of TV commercials, pat it into shape on a thick towel and let it dry. The result is a clean, soft, fresh-smelling sweater -- much nicer than something that's been doused in chemicals and strong perfume.