actually, i find it quite the opposite, save for the G4.
The tray-load are easy, just take off the bottom, and then pull out the tray. The CD is just fixed to it, and easy to get.
The SLOT LOAD is a bit more complex. you gotta almost tear it down to get at it.
The G4 iMac is quite easy, having done both optical, as well as hard drive replacements.
I just hate having to work close to the CRT when you work on the slot-load. The tray-load is pretty closed off from the bottom.