FOUR Apple computers. Yes, four. Soon to be three though, but still.
2010 iMac - the ultimate one. Only thing it doesn't have is a SSD which I've found not to be necessary with this much raw power. This is basically my center controller. It manages all of my various hard drives, external and USB/SATA/IDE drives, collected over nearly a decade of computing. It's helped with duplicate reconciliation and reorganizing. End goal is to have a single drive of some high capacity that holds all of my content. Tried a NAS but they're not fast enough. iMac is also my processing machine for videos as then I can record high def video and let the iMac do the the rendering while I'm not at home. iMac is also my backup if I'm working on the Big Apple and it's down for the count - upgrading something or some other - I can still compute on the iMac.
2011 17" MacBook Pro - the 2.2 version, maxed out RAM. The "Big Apple". SSD. It's my primary computer. It goes with me to work and I use it on appointments. Could it do the tasks of the iMac? Sure. But tethering a bunch of USB drives to a laptop is clunky. Also the Big Apple handles the VM demos I have to do for my job very nicely.
2010 11" MacBook Air. Base model with 128GB drive. Like the form factor, but the poor thing is SEVERELY underpowered, so I'll be selling it to a colleague at work here in the next couple of weeks. Before that it was my mobile "quick notes" machine, go to a customer site and pop it out to jot down some notes. Too much money for a limited use case, which is why it's getting sold.
2010 13" MacBook Air. Ultimate model. It is bigger than the 11" and that does bother me a little, but the raw power helps. Now I can use it to power occasional quick demos or development or if I'm going on a plane ride, I can use that in the airplane tray instead of fighting with getting the Big Apple to fit. I'd still take the Big Apple as my primary workhorse, but now I can bring the Air along for the one-offs where it's not practical to bring Big Apple out.
I've been on the fence about needing three and the reality is I don't NEED three. But the Big Apple and the iMac are both critical in my workflow. The Air is a "nice to have handy" type of machine.
Some might say...
"why do you need the Pro if you've got the iMac?" Power on the road.
"Why do you need the iMac if you've got the Pro?" Delegated tasks that are better suited for a desktop computer (i.e. share management, storage consolidation, raw file processing where it will take over 20 minutes, etc), watching movies on the larger screen while working on the Pro, etc.
"Why do you need the Air if you've got the Pro?" I don't really. But it helps in certain situations where carrying the Big Apple doesn't make sense, i.e. quick visits to a customer site. I'm still a little on the fence about the Air though. In theory I could go with a 13" MacBook Pro, high end, throw a SSD in there and still come out higher spec than the Air. I might very well end up going that route. But in summary, it's nice to have the third, smaller, lighter machine for the one-off stuff, the powerhouse mobile for the heavy lifting on the road, and the powerhouse desktop for the delegated tasks.