Its no different from the standard Xbox except for the bigger HDD and an HDMI interface as opposed to component. The bigger HDD is available seperatly anyway, and the HDMI interface doesnt really offer any advantages except consumers in general cant see beyond their own arses and believe everything the media tell them, and therefore they think it needs HDMI to be HD Ready or provide an HD signal, which is totally untrue.
Interestingly, it doesnt include an HDMI cable....
And finally, 120GB aint really enough capacity for much HD content anyway, the SkyHD v1 box (which was released last July) uses a 250GB HDD and even that is condered a bit lacklustre by many for HD content, but it was huge when it was released.
Im not sure if the Xbox uses 2.5" HDD's, but even so 120GB is far too small, Hitachi have recently released a 250GB 2.5" Travelstar HDD for £140 retail which uses perpendicular recording. 120GB 2.5" drives are only about £55 retail cost now, so MS are making a small fortune on them selling them at £90. If (i dont know, I assume its a 2.5") its a 3.5" drive, its a pretty much pathetic offering.