Seriously, I can't help but wince whenever I see the quality of the tray loading iMacs compared in positive terms to *anything*. I've never owned a slot-loader, but wow, they must be awful.
(Maybe my problem stems from a tendency to conflate "quality build" with "quality design". I suppose other than the stupidly fragile hinged door over the ports the tray-loaders are at least mostly made out of sturdy materials and reasonably "well built". But the internal design is such a hack. Completely, irredeemably, south-end-of-a-north-facing-mule bu** ugly through and through. And it's not just physical; technically the machines are essentially Beige G3s in drag, with most of the weird glitches and gotchyas of that machine plus a few of their own. They work okay under "classic" Mac OS but once OS X enters the equation they just flat-out suck.
For whatever quality problems the slot-loaders have at least they're a clean design.
Of course, both were ultimately designed to be disposable. It's pretty impressive to find two abandoned ones that both have working monitors. Both models were infamous for blowing out their flyback transformers/analog boards in droves after they hit three or four years old.)