Hooray!... got nVidia driver working. How do I enhance nVidia's advance functions?
 

I'm using Debian testing with kernel 2.6.15-1-686 and successfully installed nVidia's official driver.

I'm using Gnome 2.14.

Is installing nVidia's driver enough to use all it functions or do I need to add something in xorg.conf to enhance it? How do I know that Debian is using the full video memory, which is 512MB?

I noticed that I cannot use GL screensavers and what do I have to do enable it?

Finally, how can I use MS fonts?

Thanks in advance.

Just the nvidia driver is enough to get video acceleration. To play with some more settings there is nvidia-settings that should have been installed with the driver.
Check the output of glxinfo and make sure direct rendering is enabled. Did you edit your xorg.conf to use the nvidia driver instead of nv?