The problem with computers today is disk space. Good computers today are reasonable specs combined with SSD drive technology. My hardware advice is basically; just get a MacBook Air on your budget and resist the MacBook Pro unless you want to store a lot of photos and songs, in which case you remove the superdrive and load it with the biggest HDD you can afford. Never let the budget move you off of SSD, instead drop the secondary HDD and go with the cheapest 128GB Air. But of course people would like to potentially store all their photos and songs in one place and 128GB isn't enough after 3 years of photo archival. Just because you don't currently have a huge iPhoto library, everyone aspires to become a domestic documentarian and hates the idea of running out of disk space.
The way to solve this is to turn filesystems, or at least program file management into the problem domain of databases. Make the filesystem eventually and discriminatingly consistent. Apple is taking steps in this direction with iTunes Match, turning your collection into an iCloud enabled and legalized semi-streaming service. The first time you play a song in your iCloud library it gets downloaded, but the bulk stays in the cloud. I imagine you could then push things in and out of "offline mode", or make iTunes manage it. Apple needs to do the same with iCloud.
This also solves the other problem with hard drives, their unreliability.
Let's do this at a lower level. iCloud could continually scan your SSD drive for files you only rarely seek. I would not be surprised if Apple were working on an iCloud solution that jumps in when you run out of disk space and pushes things to "online" mode. Algorithms can easily detect files that do not need fast access. OS X apps with could access an API to correct false positives. Merge Spotlight, Disk Utilities and Time Machine into one interface to manage this.
