Well, I went w/ the 14" over the 12" for several reasons:
1. Most importantly, I bought it off eBay 1-week old for $300 less than new. Yes, it's the latest 1.42ghz version, 60gb, 512mb, superdrive.
2. My wife and I take alot of roadtrips, and we watch movies on it. The 14" screen will be nicer for that.
3. Having the portability of the Superdrive, especially as nice as it is now, is great.
4. Did I mention I got mine practically new for $300 cheaper than new?
Coming from a 12" dual usb model, the 14"'s footprint is a small adjustment, but it's worth it for me personally.