I wonder (exception made for you and a few other blocks here on MSFN, that I would define "advanced users" ) what is the actual *need* for 64 bit
I'm not debating against the "advanced users" part. As for a need, for me at least, it comes from needing to run x64 apps for memory and/or speed reasons (Photoshop, SolidWorks, x264, 7zip/winrar, etc) and needing a lot of memory (both for a single app, and for several heavy-ish apps at once). Plus many other other factors, like new video cards having a LOT of memory, having to develop for x64 OS'es, having to run 64 bit OSes in VMs, etc.
As often happens MS own articles and numbers within them are deceiving
Not really. XP x64 sucked really bad and it came out years late (bringing WAY more problems than benefits) so of course no one adopted that. When Vista came out, a lot of people (including me) didn't bother yet, as driver availability for x64 OS'es wasn't quite there yet (HW vendors not re-writing drivers for all their older devices), RAM was a bit more expensive so 4GB+ wasn't all that common yet, and there weren't so many x64 apps either.
With Win7 things are much better all-around, and it's finally getting some adoption. We went from "avoid" with XP x64, to "if your HW supports it and has drivers" with Vista, to "preferred" with Win7, and it'll keep going in that direction.
Of course the "overall" figures look low when you include every single machine built in the last decade like you did, when x64 only became "mainstream" with the Win7 release a few months ago. The percentages you show are very promising and will keep climbing pretty fast as supposedly 3/4 of Win7 PCs sold at retail ship with the x64 version (it might even go up as even the newer Atom CPUs now support x64)
XP came out in 2001, or more exactly 3257 days ago. Win7 was 274 days ago. The "mainstream x64 OS" has only been out for 8% as long, and it already has almost as much market share (7% by your math) -- or 13% for x64 overall. If you only include PCs that shipped in the last few years (Vista/7), we'd already be up to 33% adoption overall (and rapidly increasing) which isn't bad at all. By the time Win8 is mainstream (in probably 3 years or so; it's supposed to be the last one with a x86 version too), it'll likely be around 50%.
the large majority of apps available/in use are 32 bit, or has this changed lately?
That hasn't changed yet, but a LOT applications are now also getting a native x64 version (even MS Office 2010 now does). And a lot of users are quickly moving to the x64 version, like for Photoshop, where a poll on John Nack's blog back in 2008 showed ~40% of Photoshop users running a x64 OS already
, with another 20% or so to switch within a year (again, that was 2 years ago). And it's understandable because it can make for a huge difference in speed too
. Also, more and more apps are becoming x64-only, namely Win 2008 R2 (even if you only intend to use it in a VM), Premiere Pro CS5, After Effects CS5, Exchange 2010, etc.
I don't see a reason to stick with x86, besides for those who are completely stuck with "legacy" devices.