I'm imagining something a little bigger than a shuttle or a cube, but yes, the general idea is definitely smallish. It should be as easy to get into as a Mac Pro, not as nightmarish as a Cube or Shuttle.

Even if they added a third PCIe slot and made it about half the size of the Mac Pro, the idea is that some people would like this type of smaller desktop that's not using uber-expensive server-class processors and memory.

For now, Firewire disk access (esp. FW800) beats the pants off USB. I'm not going to hold my breath for a Mac with an external eSATA port.

In an iMac revision I'd like to see an Expresscard slot as well. Mainly for using with adapters to insert camera memory cards. We had prototype machines at ATI just before they introduced the (then) new style white iMacs with iSight that had a built-in multi-format card reader. I still don't know why the reader was dropped from production machines.