It's got entirely new guts you twit.
You're acting as if the mobo hasn't changed at all. The list of improvements is actually quite long:
Fastest system bus in the industry (167Mhz)
True DDR support for a sickeningly high throughput of 1.3 to 2.7 GB/sec. depending on what component is currently speaking.
Dual Optical drives
We get our 4th RAM slot back.
Entirely new motherboard with features reminiscent of Hypertransport.
Dual onboard HD controllers for a total of 6 drives hostable, stock.
Improved low-noise cooling.
Audio input @ VERY acceptable tolerances.
New faceplate, love it or not it IS an improvement.
Audio output on the FRONT. Finally!!!
PCI slots moved to the top of the case where they belong so there will be less cable crossover and less reaching over the CPU to add cards.
Speaker moved to the top of the case where you may actually get decent sound out of it.
Latch assembly reworked to have more metal parts for reduced failure rates.
Ethernet and Modem ports moved into a more logical arrangement which will be easier to describe on the phone to technophobes.
Did I miss anything?