From talking to players in my old school campaign and players at the local game shop, I've decided that, locally at least, the main divide between liking old school D&D and new school D&D seems to be the player's opinion of combat. Players who like fast, narrative combat are interested in older version of D&D while players who like using miniatures and battleboards for tactically detailed combat are interested in newer versions of D&D.
This divide seems to be nearly universal among local D&D players I've talked to and seems to be a better "determining factor" for interest in older version of D&D than other factors (such as save or die, level drains, character skills vs player skills, or GM fiat) I see talked about on RPG forums and blogs. Players who enjoy the long, tactically rich combats of 3.x and 4e show the least interest in trying older versions of D&D while players who do not like long, tactically rich combats are much more open to trying older versions of D&D.
Is this universal? I have no idea, but I've discovered recruiting players locally is much easier now that "discovered" this.
[Don't forget that rare Traveller fanzines (Working Passage & Imperium Staple) and the RPGA limited edition AD&D Modules R1 (To the Aid of Falx) and R2 (Investigation of Hydell) are available (for Cancer Fund Donors) -- addition to the usual PDF downloads every donor has access to. There is still plenty of time to make a donation and get in on the giveaway which ends at the end of October 2009. Thanks much to those who have already donated.]