I had the opposite reaction. He was fairly uninteresting to me until he had his drug problem. Oh well, boats float.
(Although, my favorite episode of the show for a long time was one featuring him that didn't relate to his drug problem, titled Pine Barrens, the one where he and Paulie are running around in the woods after the Russian they might have killed. There's a great line that Paulie mishears from Tony over a bad cell phone connection. Although, come to think of it, Christopher's drug issues might have played a little role in the episode.)
Tony Soprano: [over the phone] It's a bad connection, so I'm gonna talk fast! The guy you're looking for is an ex-commando! He killed sixteen Chechen rebels single-handed!
Paulie 'Walnuts' Gualtieri: Get the fuck outta here.
Tony Soprano: Yeah. Nice, huh? He was with the Interior Ministry. Guy's some kind of Russian green beret. This guy can not come back to tell this story. You understand?
Paulie 'Walnuts' Gualtieri: I hear you.
[the telephone connection is lost - Tony swears, and Paulie hangs up]
Paulie 'Walnuts' Gualtieri: [turning to Christopher] You're not gonna believe this. He killed sixteen Czechoslovakians. The guy was an interior decorator.
Christopher Moltisanti: His house looked like shit.
That episode was so funny.
Great episode and Paulie is the best, he and Chris play well off each other.