The Start menu, for a start! Hitting the windows key, typing "remo"+Enter to start Remoteverbindung, windows+"word"+enter etc. It start the apps much more quickly, no more searching through menu after menu or having to uncover the desktop.
It feels like a real OS, I think XP's biggest problem is that it either looks like Fisher Price or Windows 95, neither make it feel modern or inspire confidence.
I connect to about a dozen different networks on my laptop, I've never even seen what you are describing...

Hmm, I click on the "don't warn me again" option on that dialog.

I haven't bought a machine with less than 2GB since 2004, so it hasn't been a problem... In the office, we have a few machine still running XP SP3 in 512MB RAM, they are unbearably slow, especially if you try and open more than one app at once!
I had a C2D, 3GB Win XP at work, it was clocked higher than my iMac, but Vista ran quicker and more smoothly on the iMac! Same with the Core 2 Quad, same clock speed, ran Vista smoother than the C2D (okay, it had 2 more cores, but the general apps I used didn't really take advantage of them).
I'm the other way round, I find that it is the little improvements in Vista that allow me to work quicker and more efficiently... I pretty much skipped XP, I switched to Linux, because I hated XP, I switched back to Windows on my PC when Vista SP1 came out. It is just so much better than XP ever was, for the way I work.
I'll probably upgrade to Windows 7 on my Vista machine, OS X is already on Snow Leopard, it is noticeably faster!