I still think that is the most beatiful/clever/stylish computer ever made, probably well ahead of its time (it shipped before even the first Mac OS X release).
I bought one and loved it. I am not enough of a tinkerer to have upgraded it as others have done and eventually had to sell it to get a faster machine, build I do miss it.
Its high points were its clever core design, which made upgrading RAM and the internal hard disk very easy), its total coolness (especially when combined with an Apple Display), its utter silentness, its compactness.
Its low points were its beefy price, lack of upgradeability (especially the non-standard, low performance ATI graphics card, which was very difficult to upgrade and didn't support Quartz Extreme).
Commercially, it probably deserves to be called a failure, but I think it is a testament to the better qualities of Apple as a tech company: innovative, daring and very cool.
July 7, 2001: G4 Cube Discontinued