I particularly like the "Aluminum doesn't rust" argument for buying one, for those of you who compute outdoors in a thunderstorm. The bottom line is that they're definately cool looking, but I discount the "heat dissipation" argument as well. You should have enough well-placed fans to exhaust any heated air before it has time to stick around inside your system.
I can see the "lightweight" argument, but only if you're a partier who drags it around everywhere you go.
Otherwise, I don't see the ROI (return on investment). All of the cool-looking, shiney aluminum cases I've seen are woefully inadequate for my requirements (including the Lian, Antec, etc). I'll stick with my $600 Chenbro double-wide server pedestal with dual, redundant, hot-swappable 400-watt power supplies. Fourteen (14) drives. Ten (10) stock fans including a 120mm, two 92mm, six 80mm and a 60mm. Plus I can practically sleep inside the thing with it fully configured.
Sure, I'd love it even more if it were aluminum, but then I'd feel really bad letting my artist-wife airbrush the snot out of it to make it one of a kind.
Sort of defeats the purpose.