For me, a replaceable battery is the most important factor. With my level of usage, it's not a question of if but rather when I'll need to replace my MacBook Pro battery.

It used to be so damn easy with my 2006 MBP. Pop the old one out, pop a new one in, literally seconds to replace. You could even carry an extra battery with you when traveling.

Now battery replacement is a giant PITA. And Apple wants you to mail the machine to them and be without it for days instead of getting onsite same-day replacement. I hate this situation.

Apple desktops also used to be more repairable. I remember Apple sending me an iMac G5 midplane, which was basically the "guts" of the computer, to replace at home. You could do fan and power supply replacement too.