Google again

Our google ranking has magically improved almost overnight. I’m not going to complain about that , I just wish I knew why our site sometimes vanishs completely.
Interestingly enough Google has now learnt about our domain aliases, so all the results point to one domain, which makes more sense. We aren’t being penalised as we don’t use doorway pages or any other “tricks”.
It has also “learnt” the relationship between me and the company site, possibly due to my email signature appearing in indexed mailing lists.
I also came across this funky little tool that supposedly outputs the PR of a page:

I’m not sure how accurate or useful it is, but it’s definitely interesting.
If you look at this entry on the site’s main page it reflects the blog’s PR, while the entry on its own doesn’t seem to have registered with Google just yet, which is hardly suprising.
  Google Hacks Exposed: Improving Your Rank on Google