On this model, Apple got carried away and forgot they were making a computer and that computers break. The screws, which give it just that right touch of industrial design are almost an inch across, but the hex sockets are narrow and shallow, making them prone to stripping. And stripping them is exactly what the service people did when I had it in for a recalled video board. I had to drill two of them out, not a pleasant prospect on a machine that is essentially a thin shell over a bare CRT.
Once you get inside, things get worse. With the power button around the side instead of in front, just taking the case off means stretching the delicate wires to the power button to their limit and then unplugging them one-handed while you hold the case in the air with your other hand. And getting to the hard drive, easily the most frequent point of failure, requires discharging the CRT and disassembling almost the entire machine to get at a unit that is locked away sideways under the "digital board."
The thing is, it didn't used to be like this. Apple engineers used to put effort into making case designs functional, as well as good looking, whether it was the pluggable performa chassis that anticipated modern blade servers, or hinged power supply mounting brackets of the Quadra and early PowerMac cases that nearly doubled the effective working room, or the fold-out sides on the Bondi G3s. Of course, I can't speak for the original iMac, and I know that space is tight in the "nose cone" shell, but there has to be a better way.