I've also heard one of the "benefits" of SATA was, assuming you used the special power plugs instead of the standard 4-wire one we all love (and have eight of on our power supplies anyway), you'd get hotswappability.  A vital feature in a desktop, I know. :P Supposedly, the special plug's more delicate, prone to falling out, compared with the old ones.

 

Aside:  Whatever happened to the "3.5 x 1 inch" form factor for hard discs?  It would allow an ample heatsink, letting the PCB run cool.  Having to organise special cooling on ordinary 7200rpm desktop drives seems a bit absurd.

 

For speed:  Notice even that expensive, "ultra fast" WD Raptors don't even sustain 66Mbps.  That's the celing on the UDMA-66 standard (two generations of UATA ago).  The interface doesn't bottleneck right now, in fact it rarely does.