You should not need to be messing with permissions in this way. And Lion shoudln't be any different than Snow Leopard in any material way here.
Geoff's initial problem seems related to placing the Lightroom application at the root of the hard drive, instead of in the /Applications folder. I can't figure why that would be the case.
I would suggest NOT changing permissions on ANYTHING unless you're having problems. And in case of problems, it is much more likely that something else is odd (i.e. you've placed the catalog somewhere other than the Pictures folder in your home directory which is the default), than that any permissions need tweaking.
I'll note I have never, ever, needed to modify any permissions like this to use Lightroom on Lion. It's not something that's necessary under normal circumstances.
