My mother has been struggling with an old, old mac mini for a while, and decided to go all-out on a new Air rather than upgrade the RAM and the hard drive of the mini (good call). Here are a few experiences with the purchase and setup.
1) 4GB of RAM and a 128GB hard drive are the bare minimum most people with a multimedia collection need. This costs $1199 for an 11", and $1299 for a 13". Don't buy the cheapest model, but it's not worth springing for the i7, either.
2) In an odd experience for an Apple store, the worker kept trying to talk her into a Pro over an Air. He kept calling the Air a "secondary computer," saying it was only for travel, and talking about everything that was missing. Maybe he was new, and just working off the key points on a sales sheet. I finally told him "Look, her big gripe with the mini was slow disk access times, and she wants to be able to fit this thing in her purse." I think he was genuinely trying to be helpful, but he reminded me more of a Best Buy guy than Apple.
3) The one downside to the Macbook Air is that it doesn't have a firewire port for transferring files. Because my mom wasn't backed up to an external drive, we did the migration over Wifi. It was painless, but did take about 5 hours for 70gb or so of data.
lf/when I get another computer, it will definitely be a Macbook Air. The only things I wouldn't trust it with are streaming huge videos above native resolution (say, to a 1080p external monitor), and gaming. For everything else, the SSD makes it seem faster than even the speediest iMac, and it's really the perception of speed that affects how people experience their computers.