The odd thing is that it shouldn't be much of a hindrance (if any) regardless of whether you've been kb or mouse orientated- imo. The full page start menu gives a lot of scope once you downsize/cull the tiles, and as you say, the desktop is only a click away...and how many applications/services can't be pinned to the start page and/or given a shortcut/pin to taskbar treatment with the desktop? After adding a two dozen or so must haves (Resource Monitor, Performance monitor, Regedit, assorted admin tools, Doc's etc.) virtually anything becomes a one or two click operation even if you're not conversant with kb shortcuts. Most of the admin tools (Control panel, Computer Management, Task scheduling etc etc.) are already available -all that's needed is to click the Metro Search -assuming you've checked the Show Admin Tools option I assume.I think this is more of a problem for 'click' generation than for people who grew up using 'keyboard' as primary input device
From a personal PoV, I don't find it any more difficult to use than Win7 (easier in some respects). The functionality is little different from previous Windows iterations, and for the first time ever, my 70+ year-old parents aren't totally bewildered and intimidated by exploring their home computer- I can't see how this is a bad thing.
As for performance, I'll reserve final judgement until both the Win7 and Win8 installs have had 3-6 months of usage. I have baseline performance for both from the clean install. I'll compare again once the systems have had a chance to get ravaged by the usual barrage of updates, programs install/reinstall, and general wear and tear.