I really like the idea of not having an optical drive.
I use two computers for design about 3/4's of each day and I can count the number of times I've needed to use a CD/DVD drive on one hand.
Otherwise, there are so many more convenient alternatives that don't require me having to swap Bluray disks for backups or carry discs in shelves.
Backup: Networked drives/external HDDs/online storage
Transferring files: USB Keys/online/external HDDs
Music: Download from Amazon/iTunes
Movies: Use my PS3/Stream from online
I would be more than happy to use the space for some of the suggestions in here and have an external optical drive for rare times I've needed it. This is especially true if they used the space for an additional or larger battery, more memory card slots, bigger motherboard... That would accommodate the 99.9% of the time I'm on my laptop, versus the 0.1% of the time I've ever used the optical drive.