I think it would be a good idea to do this (anything to increase loading times and save bandwidth is a bonus) but only if there will be no side effects. If it's possible that stuff will break because of it then we aught to wait for a slightly more major revision (1.2 perhaps) where other stuff may need editing too. People can always use the compression/etc addons in the meantime I guess?
I tested the packed version (no gunzip) and there is a minor bug. Prototype and scriptaculous are not meant to be packed because of the use of global and because of its poor syntaxes. It might be packable, but the code should rely on a packed version. Plus in the core it will just load time for some admin pages.
I think we should just update it, and use an add-ons to use a packed compressed version.