Anyone is welcome to correct me about it, and please do, if I am wrong.

In what I can conjecture about it: It should be that GMail would export vCard files.

vCard files can be imported , even into PDA and cel-phone address books, in addition to those of the address books of the aforementioned, named software applications.

FYI: In the domains of Linux, OS-X, and (presumably) Qtopia(r) — regarding contacts, scheduling, and synchronization between devices:
KDE PIM works
GNOME Evolution homepage

Like as footnotes:

I’ve heard that KDE and GNOME can work with MS-Windows. I’d guess it wouldn’t be as snazzy as with Linux, but I’ve heard it could work. Cygwin might be required, for such. though I haven’t checked it for this.

I suggest Ubuntu as a first desktop Linux OS. Their LiveCD might be right cozy to use.

I use Debian myself; Ubuntu is based on Debian, is updated more frequently (In the Debian release process, Debian developers take a while to ensure that the whole OS works right, but I trust that it would work fine in Ubuntu, regardless of this difference in policy) and Ubuntu may seem (speaking of sofware and sites) to have a kinder face to it.

There is, also, KUbuntu, such that is based on Ubuntu and uses KDE in preference to (perhaps in exlcusion to) GNOME.

(I have heard that Ubuntu developers prefer GNOME in exclusion to KDE — not that I would, honestly, but they do. Debian includes both, comprehensively. )

Of course, It is up to the user (or the admin) ultimately, to decide on the window-manager/desktop-environment and the OS

KDE is well-liked by people. The KDE window manager, specifically, has a comfortable, common appearance/look-and-feel to it. KDE seems to aways run pretty efficiently on older boxes, also. (GNOME’s flashy pixmap and SVG-based themes will lag older boxes, though not all GNOME themes use pixmaps as such)

Some might still prefer GNOME (e.g. gnome-panel and Nautlius, which are some nice stand-alone applications, however, not requiring an explicit adoption of any one “desktop system”)

I use Sawfish as a window-manager — neither KDE’s desktop nor Metacity (favorite of GNOME) and not Enlightement (a.k.a E), Icewm, WindowMaker, GNUStep, … — and some KDE apps and some GNOME apps, and maybe some using neither GNOME nor KDE ‘libraries’ and not using QT (KDE) or GTK (GNOME) as the GUI toolkit; gratefully, when you’re familiar with it, it works out pretty nicely.