Does everything work perfectly with the drive except for the noise it makes? If so, I wouldn't worry, as it is normal for the drives to make some noise like that. For me it wasn't that much of a surprise because I'd been using slot-loading DVD drives prior to getting my PowerBook and it certainly isn't that much louder than a normal slot-loader, but I've seen people who've only ever used tray-loading drives pop their eyes out when they hear what they think is their favorite disc being chomped!
If the discs are getting spit back out or not being read, then I'd pursure AppleCare's assistance with it. Otherwise, if everything works fine and it just sounds noisy, it is unfortunately "normal" for that drive.