From the review of the Mesh system Marc gave above:
That's the only real downside to these SFF machines - limited expansion capability. On the other hand, the Mesh seems to have pretty much everything you'd want anyway, but it's worth thinking about future upgrades. (Not sure, for example, if the SFF machines will support more than one optical drive for copying, or more than one hard drive for optimum video capture. That said, from that point of view, they're probably no worse than an equivalent laptop).
One thing you do lose with a small case like the CubeX's is any real scope to expand the PC by adding new components.
Premiere Pro, Encore, Photoshop, Ulead VS6, WXP Pro, Core 2 Duo, 2GB, 2 x 250GB SATA3 drives, 2 x 250GB USB 2 external drive, DVD writer, GeForce 7300 GS 256MB
The biggest fool can ask questions that the wisest man cannot answer...