Why I went for the solid state drive:
1. i have no requirement for a lot of data storage on my MB Air. So, the 64Gb limit now on the SSD is fine. Everything the Air knows in the morning will have come from an archive. Everything it knows by nightfall will end up in an archive. What's on there is transient and doesn't require a lot of context to serve my needs. There will be plenty room for extracts from my other machines' iTunes libraries. Throwaway playlists. Some TV shows.
2. speed, less wear and tear on the thing having to wake up two or three dozen times a day to find out what the heck I want now. Kinda like a nano on a lanyard when you're trying to listen to a long album but the phone keeps ringing. The nano doesn't care how many times I hit pause and play. Drives are cheap enough to replace, but if they aren't there they can't break down.
3. "Evolve or Die," we always used to say at the job. Take it to the next level. There will be some application-centric spinoff from using flash as startup storage. I don't know what it is yet but Apple probably has more than a clue and I want to see what happens next. The ticket to that is buying into the tech as it's rolled out. I signed onto that long ago, I know the drill on risking early obsolescence by early adoption and it just doesn't faze me.
4. One of my uncles told me a long time ago there can be times when it's better to spend a hundred bucks than to break a twenty dollar bill. I have come to know exactly what he meant by that, and have acted accordingly by putting $3k into my MacBook Air config.