Assembly still makes my head hurt (...working on it - see Andrew Harrington's Pip [.zip of .py and .txt files], a Python application that lets you play with assembly - yes, I know that's backwards) but disassembly is fun.
Didn't realize this until now: The XO has a couple of extra screws embedded in its handle in case you lose one - they're screwed into otherwise nonfunctional plastic nubs. Now that's thoughtful design.
I've also been telling people that if your laptop's hinge breaks, you can still use a headless laptop perfectly well because the motherboard's right behind the screen. I finally decided to film it; the video is here. I point out the three cords attached to the laptop (power, USB keyboard, USB mouse), demo all three working, then lift the laptop up to show the hinge is an empty tube of metal with wires dangling from it (the keyboard/bottom-half of the laptop is shown half-disassembled in the background).
In contrast, my computer from college was rendered much less portable this summer by having its hinges (a common failure point in laptops in general) rip off, leaving me with an unintentional tablet - a maze of dangling monitor wires were the only thing keeping the screen connected to the rest of it.
It's also fun to freak bystanders out by pouring some water on the membrane keyboard, which is a sheet of rubber set on top of a multi-layer PCB screwed onto a thin metal backing. I have no idea how the PCB works. Pressure sensitivity?
I found the monitor-half of the XO to be easier to assemble/disassemble than the keyboard-half, although that could be because I've taken apart the former several dozen times by now and took the latter apart for the first time just now. The white bottom panel (with the two hold-in-the-battery latches) is a little tricky to pop back in; it took about 30 seconds of futzing the first time, so I made myself take it out and do it again faster. Then, after I'd finished reassembling everything, I realized I'd popped out the spring-loaded latches that hold the laptop locked. So I had to take everything apart and put it back together again. It was considerably easier, and I got the white bottom panel in in about 3 seconds.
Getting the hinge screwed back in (connecting the two halves) was mildly annoying. I eventually realized I could magnetize my screwdriver and do away with the "can I drop the screw into the right place from 1cm up?" game. There's a strong magnet on one side of the keyboard (and a hall effect sensor on each side of the display so the laptop can sense when it's closed and in tablet mode and turn off keyboard hardware accordingly) and a few strokes of screwdriver-on-magnet made life much easier. (Note to self: next time do this before sealing up magnet behind bottom of laptop case.)
My fine motor coordination skills need some work; I'm a horror at surface-mount soldering, and my control with the multimeter probes tonight was... not good (much shorting ensued). Of course, the freezing weather (and the inadequately heated room) probably contributed to the butterfingers somewhat - my hands are constantly cold and stiff - but maybe I should take up those exercises little kids do to learn how to manipulate their fingers... handwriting practice? Embroidery? Detailed electronics kits and a fine-tip iron?
It's pretty obvious which one I'm going to pick. ;-)