The new top of the range iMac may now be powerful enough for location-based editing:

CPU: Up from 2.33GHz to 2.8GHz!
Built-in 7200-rpm SATA: Up from 750GB to 1TB
Internal display: Still 1920 by 1200
External video: Maximum still 1920 by 1200
No eSATA, no improved external video connections.
But the new keyboard now has USB 2.0 ports.