Hmmm, 8GB or 30GB for $249? No brainer.
8GB in a small slim form factor that's immune to shakes and vibrations vs 30GB in a slightly larger form factor that needs to be handled far more carefully.
The question at this point is based upon which stores your music collection. If your music collection can comfortably fit in 8Gb, and I suspect most people's can, and you're not planning to use the extra space for anything else, then the 8Gb flash-based system is objectively superior.
If you're interested in lossless music formats, use it to watch movies and TV programmes, or plan to use it to transfer data, or just store your pr0n collection, then yeah, the 30Gb version is the only option that will work for you, though it may even be too low in the capacity stakes.
I'm seriously considering getting a nano myself. I've been using a 2G (touchwheel, no dock connector) 10Gb unit for a while, and it's generally got more space than I need. I don't want to watch movies or TV programmes, I'd never have the opportunity to, and certainly wouldn't want to watch them on a tiny screen. AAC and MP3 are perfectly fine in terms of quality, my headphones distort the sound more than the formats do. I, in practice, never use the iPod for transferring data, and an MMC/SD card or burnt DVD is better for that anyway in my experience. So there's absolutely no reason on Earth to get the 30Gb model. I'd be buying something that's less solid and larger, for no material benefit.
YMMV.