Flew to Lisbon early Friday morning with coworkers, saw some sights, got plenty drunk and afterwards a two day long splitting headache caused by neck pain (luckily painkillers helped at least the first day), ate several servings of absolutely lousy food (you get the idea that the Portuguese aren't big on vegetarianism), thought the city was really beautiful, was extremely happy to get back home at midnight yesterday.
It's true that users shouldn't have to know how things like the X Window System clipboard/selection mechanism works. But really, they don't have to: as the freedesktop.org documents points out, users are really expected to use the CLIPBOARD mechanism which works pretty much like clipboards on the competing platforms and live happily without the select/middle click thingy. Jarno, you only have this problem because even without an unix beard, you've been using these things long enough to know the PRIMARY selection mechanism.
I expect Jarno has heard about this already, but just to nitpick a bit: in X Window System, selecting a piece of text does not normally copy it to the clipboard, despite this being a widely-held belief. Or well, it does, but it's not the only clipboard, and in X parlance, it's usually called the PRIMARY selection. There are three standard selections: PRIMARY, SECONDARY and CLIPBOARD.
To copy things to "the" clipboard — the CLIPBOARD selection, that is — you usually have to invoke an explicit copy operation, typically via the menu choice Edit -> Copy (or your localized equivalent) or via a keyboard shortcut, typically Ctrl-C. You might notice some similarities to certain other systems. And the same goes for the opposite actions: middle clicking only pastes the PRIMARY selection. To paste the contents of the clipboard, Edit -> Paste or Ctrl-V is typically the way.
For more information, see the explanation at freedesktop.org.