Wouldn't it be nice if the Thunderbolt Display had an optical drive? Lack of an optical drive is one of the few things that makes me nervous about going the MacBook air route anytime soon.
If you like watching DVDs while you are mobile I would definitely not recommend getting a PC without optical drive anytime soon – for obvious reasons. If you don’t, I really see no reason not to ditch the optical drive. All other use cases seem to be handled well enough by emergency external drives.
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† Like this one: http://www.amazon.com/Samsung-External-Optical-SE-S084D-TSBS...
With RipIt.app set to auto-rip every inserted DVD and eject it it's no hassle.
- ripping CDs of rare or out-of-print music.
- burning CDs/DVDs of photos for friends who don't have a USB drive.
- reading old CDs I have, like a CD of BeOS.
But I use it infrequently enough that maybe a peripheral is the way to go.