Packages differences between Ubuntu versions (i.e.: Hardy Heron versus Jaunty Jackalope)

[Oli D]

Hi,

I'd like to know what are the differences between the different Ubuntu
versions. The way I understand
it, the main differences lie in the packages (which version is
available in the version's repos, etc.) plus some few
minor changes such as the Private or .private or private or whatever folder.

In short, what I'd like to know is if, for example, I "echo 'package
hold' | sudo dpkg --set-selections" and then
dist-upgrade, are there possibilities for the system to break? (For
the record, I'm willing to hold the main X.org
package from Hardy and then upgrade to Jaunty since I want to use the
nvidia-177 driver on Jaunty).

Anyone knows if my idea could work or if it's likely to break the system?

Regards,
Vhann