Nope, I use an external USB drive on the very rare occasions when I need it. Then again, on my old laptop, I had no idea that the drive was broken for almost half a year, so rarely did I use it. Using it to play DVD's can be cumbersome on the go, with that extra piece hanging around, but many DVDs now come with a version of the movie built for portable devices, which you can copy over to the netbook and watch on the go. If you're using Linux, Totem movie player plays just about everything.
Caveat emptor: Netbooks aren’t for everybody and definitely not for every computing purpose. Here’s a good Wired article on netbooks:
http://www.wired.com/gadgets/wireless/magazine/17-03/mf_netbooks
What do you do if you have to reinstall Windows?