The Mac Mini is an iBook in disguise, so to speak.
If no surprises happen, the AOpen Mac Mini clones will go down with all flags flying in a price comparision:
Mac Mini 1.25 Ghz G4, 512 MB L2 Cache
512 MB PC2700 DDR SDRAM
ATI Radeon 9200 32MB
40 GB
1 FireWire 400, 2 USB 2.0, 1 10/100BASE-T Ethernet
DVD-ROM/CD-RW
OS X and some Apple software
56k Modem
$499
Mac Mini 1.42 Ghz G4, 512 MB L2 Cache
512 MB PC2700 DDR SDRAM
ATI Radeon 9200 32MB
80 GB
1 FireWire 400, 2 USB 2.0, 1 10/100BASE-T Ethernet
DVD-ROM/CD-RW
OS X and some Apple software
WLAN 802.11b/g
Bluetooth
$599
Barebone MP915-C (Celeron edition)
roughly 320 Euro = $379
Cheapest possible system, proposition of heise.de, early November:
"PC Mini" 1.4 Ghz Celeron M 360 1 MB L2 Cache
512 MB SO-DIMM PC2-4200
GMA 900 Graphics Chipset w/ shared memory
40 GB
1 FireWire 400, 1 USB 2.0, 1 10/100BASE-T Ethernet
DVD-ROM/CD-RW
no OS and Software
roughly 595 Euro =
$706
Until proven otherwise, I think it is possible to put a faster clone to gether but it will cost more than the Mac Mini. Got to pay the form factor, heh.
Sources:
http://www.apple.com/macmini/specs.html
http://www.heise.de/newsticker/meldung/65660