(As opposed to my previous failed attempt in May. )

Installing Debian Sid's gotten quite easy with the Debian-Installer. Here's a step-by-step review.
  • With a broadband Internet connection, it's easy to install over the 'net. I downloaded and burned the Debian-Installer "netinst" CD image, booted from it, and followed the prompts (it goes fast if you've prepared your hard disk partitions in advance and know where you want / and /home and swap mounted).
  • At the installation CD's boot prompt, I chose the 2.6 kernel.
  • After installing the base system and the boot manager, the installer rebooted the system and asked what kind of system I wanted. You can choose "Graphical Desktop" (I think that's what it was) and from amongst several server options. This time, I chose not to go into "dpkg" (going through it took forever); I only chose the desktop option. At this point, the installer began downloading and installing packages from the 'net. It downloaded GNOME, KDE, and several other smaller window managers, along with a slew of software. (This took about 30 minutes.)
  • It started up using gdm as its login manager and GNOME, with the wrong screen resolution (my fault; 85Hz was probably too high a vsync setting). Personally I'm a KDE and kdm partisan. Setting KDE as the default was as simple as telling gdm to start KDE; it asked if I wanted to make KDE the default. (Nice.) I had to download kdm, at which point the package manager asked me which login manager I wanted to use, gdm or kdm. (Nice again.) To fix the screen resolution, I logged out of KDE, stopped kdm, and ran "dpkg-reconfigure xserver-xfree86".
  • Now I had Debian Sarge. To upgrade to Debian Sid was a matter of stopping X, changing "testing" to "unstable" in /etc/apt/sources.list, commenting out the "security" line, and running apt-get update && apt-get dist-upgrade. (Downloading the software took about 15 minutes.)
  • The system required a reboot to reconfigure itself for the kernel modules.

And that was it!

Unlike last time, I had no problem whatsoever with the "nv" server and my nVidia graphics card. It installed kernel 2.6.8-1-386. There's more to do -- for example, CUPS and ALSA aren't installed yet -- but that was pretty easy.