I just wrote this post about how I decided NOT to use my Air as my primary Mac, and now I've gone and changed my mind. I had a few catalysts. The main one was that the iMac doesn't do any better than the Air for Aperture, the one program that caused the Air to pause for a few microseconds. Aperture was a new purchase for me at the time, and I assumed it would fare better on the iMac. Not so. Secondarily, I read this post by Frank Chimero and reconsidered how I was trying to use the Air. With a few tweaks I've been using it alone just fine, and the iMac is up for sale (I'm wiping the drive as I type).
I was surprised when I actually looked at the disk space I use; I assumed that I'd have to keep everything on external drives with the Air, but it turns out that aside from my giant iTunes media library, I can really comfortably fit everything including ALL of my photos on the Air and have 20 GB to spare. This is because I do text and photos and that's it. No video editing, nothing crazy. Delving into what takes up space on my hard drive was extremely educational. I liked Chimero's idea of hot-swappable components (moving iTunes libraries from computer to computer is hair-raising even if it mostly goes well) and decided to keep my iTunes media on an external drive anyway, whether I kept the iMac or not, so that became moot in my decision. All my photos are now on the Air.
Time Machine? I decided not to use anymore. The few times I've needed a Time Machine backup, something has failed and it hasn't worked. Mainly it seems to spin and read "deleting backups" in the menu bar. The backups I use are the SuperDuper ones. I consider Dropbox a backup as well, because all my crap is in the cloud (I use Dropbox as my Documents folder; all my stuff goes there). So I have one external drive loaded with iTunes media and one giant one partioned in two. To one partition is cloned the media drive; to the other, the Air flash drive. I'm religious about my clones. I also have an iPod Classic to which I sync all my media including full-resolution photos, and I keep it with me, so that's a sort of triplicate media backup.
Now, another issue is that I want the laptop to actually be MOBILE and not tethered to so many cables it stays on my desk all the time. I synced my entire library to my first-gen AppleTV (such a bad choice to remove the hard drive, Apple), so I have all my music available that way. I rarely need to sync my iPhone or iPad with the computer, but if I do I will have to hook up the external media library. No big deal. This would be a dealbreaker if it weren't for Audiopress, because I do like to have a current list of podcasts on my iPhone, and I would be bitter and resentful if I had to hook up two cables every day to sync my phone. Other needs are printers and my ScanSnap, both relatively rarely used.
So really the only major changes are having my iTunes media on an external drive and having to physically plug in my SuperDuper clone drive before I hit "Copy." I can live with that. I'm not going to buy an external DVD drive just yet...I haven't used the one in my iMac for a LONG time. If it turns out I need one, I'll get one later.
Babysitting drive-wiping and software-updating is the perfect activity for someone recovering from the flu. I have about the energy span required to get out of bed, poke some buttons, and go back to lie down. Yes, I'll wipe down the mouse and keyboard of the iMac before I package it up! I'm putting a clean install of Snow Leopard and the latest iLife on it...should be sparkly clean and loverly for my lucky buyer (if you're a local and you're interested, drop me a line).