I believe sgfxi is working fine on karmic and lucid, though I don't do much testing on those. All the steps above are automated, as is card detection etc.
In other words, this is the sum total of steps you should need to run for nvidia:
cd /usr/local/bin/ && wget -Nc smxi.org/sgfxi && chmod +x sgfxi && sgfxi -c
You can do this in X, and when sgfxi starts, it will just complain about x running and exit, then you can drop to terminal.
And that's only the first time you grab it, it updates itself always to latest version when you start it, if required, so after the above, this is the sum total of steps / commands you should need to run:
the -c is for setting composite true in xorg.conf, if you don't want composite, or if it's an old legacy card that doesn't handle it, you don't need it, but sgfxi will turn that off for legacy cards automatically I think. There was some discussion of making composite default, not sure about that yet.
Must be run out of X because the nvidia installer won't permit installing while X is running.
sgfxi -B tests for and installs latest beta nvidia, if available, if it's not, it simply reverts to the latest nvidia driver for your card type.
Any failures or additional steps that might be required are considered sgfxi bugs, and should be reported to the script forums.
I'm not testing very heavily with dkms, and the modeset blacklists are fairly new and may need to be expanded, since I only use dkms for testing, never in standard use, I can't really keep up on that nasty mess.