How's Vista garbage? People didn't like it because computers were not powerful enough to run it smoothly. Run it on a new recently released computer and it will fly.
1. Slow boot times compared to XP, 7 & 8 on like hardware.
2. Worse security than 7 & 8. I shouldn't even need to mention UAC in Vista, but obviously I will. It should conjure a commercial with Justin Long and John Hodgman in your head (http://www.youtube.com/watch?v=FxOIebkmrqs
3. Atrocious gaming performance.
4. Similarly criminal battery usage on laptops.
5. The driver landscape is somewhat worse since that was the first OS that Microsoft enforced User Mode and Kernel Mode drivers forcing hardware manufacturers to hastily redo their support. However most devices that have Win 7 or 8 drivers can use those drivers in Vista, so this is more of an older hardware problem.
As to Win 7 vs 8, there are some benefits, especially now that you can boot directly to the desktop and skip the whatever-they're-calling-the-touch-interface-this-week. Notably backups, drive mirroring, and file history (essentially version control) is a snap and works really well.
You'll know when you can't get into BIOS with a USB keyboard
There isn't a single BIOS on a motherboard made in the last 4-5 years that doesn't natively support USB mouse and keyboard natively (i.e. during POST). The only situation where this would not be true is someone having disabled USB in the BIOS or a faulty device -- the latter of which would mean you weren't going to be doing anything anyway. If the former is true, a simple reset will solve the problem.
The PS/2 port really just needs to be thrown on the techno trash heap with PCI, 15-pin VGA, and IDE to keep AGP, ISA, and IEEE 1284 ports company.