Today, 12X or 18X is standard. Guys with bigger bucks go for the 24X, or the latest 32X drive. Many of us still have 6X or 8X drives, though, and these are fine. The performance difference isn't enough to justify replacing it. Before buying, you have to decide how you want to put the disk in the drive.
CD drives come in three forms.
Some drives use caddies to hold the disks. You put the CD in a caddie and then stick the caddie into the drive itself. The caddie helps to stabilize and protect the disk. Another kind of drive is one with the slide out drawer. When you press the eject button, the drawer pops open and you lay the disk in.