One of the most surprising things about the announcement of the the new MacBook Pro at Macworld Expo this week was Apple's dropping the 8x burning double-layer SuperDrive in favor of an inferior 4x single-layer mechanism.
I was puzzled during his keynote address when Steve Jobs listed the specs of the new MacBook Pro with only a 4x SuperDrive, it was surely an error I thought. Why would Apple ship a 4x SuperDrive in a machine touted as so much faster than current PowerBooks? (The current PowerBook G4 ships with 8x SuperDrives.)
One possibility was Apple was using an even slimmer optical mechanism than the one found in the current PowerBook G4 based on the slimmer profile of the MacBook Pro. A colleague went to the Apple booth and interrogated the MacBook Pro and found some interesting information: the part numbers coming up in Apple System Profiler for the 4x SuperDrives were ones we've never seen before - and no double-layer support.
After a little research we found out that the optical drives in the new MacBook Pro (PN: GWA4080M) are a slimmer version of current PowerBook slot-loading drives. Being slimmer there are some technical hurdles to cross before they can write at 8x and before they can support the double or dual-layer protocols. This was confirmed with a contact in Apple's storage division.
So it would appear that Apple is not dropping double-layer support or purposefully shipping slower mechanisms in the new MBP. Given the space limitations in the MacBook Pro these drives are probably the fastest available. Once the technical issues are resolved, later MacBook Pros will certainly write at 8x and support double-layer writing.
I think that while the slower drives are certainly a downside to the new MacBook Pro, they should not be a reason not to buy one. In time new drives will appear which will write at 8x and support double-layer and which can be retro-fit into the first generation MacBook Pro with little trouble and fairly economically - just as you can now fit an 8x double-layer SuperDrive into first generation PowerBook G4s for US$149.