"The only new standard, the USB 3 would be used to the full potential here since we have yet even saturated SATA I or PCI Express 1.1 with the current HDDs/GPUs. "
SATA-II is being already saturated by current gen SSDs and a complete bottleneck for next gen SSDs coming out soon. So yes, you don't know what you're talking about.
As for PCI-E 3.0, 2.0 has 20% overhead data and 3.0 has 1.5% overhead data. Less energy will be wasted on overhead on top of overall more bandwidth.
Win7. All those nifty UI affects also take their toll. Vista had a copy of the textures/etc needed in system memory, then copied it up to video memory. This helped reduce latency by not relying on the bottleneck between CPU and Video card. Win7 now stores everything in video memory, so any "updates" it does to your screen requires copying down the needed data to the CPU over your PCI-E, modifying, then re-uploading the changes. This will overall increase PCI-E usage, also your UI thread stalls on waiting for the data to get back from your video card. The faster you get data back from your video memory, the less CPU time wasted on stalling.
you may say PCI-E is already fast enough, but when you compare 4GB/s of PCI-E 2.0 to the 38.5GB/s of tri-channel corei7, you can see why Vista opted to just duplicate/waste the memory in order to reduce latency.