unless I use a screen-keyboard, I need to change my hands from the keyboard to the mouse and back again for this "one-click-experience". Thats stupid. My setup has "one keypress search" (ok actually two if you count whitespace), which is far more better. I use an already existing feature. My most important search sites get such shortcuts. My current prefixes are:
w : en.wikipedia.org
a: web.archive.org (link down? just paste URL, pos1 and a + space)
Best thing is, it isn't cluttered up with all that ebay or other sites. Disadvantage of course is that I have to set it up on each computer I use firefox on.