Very nice! Is your site in a non competitive niche? I just got my 2 month old URL to a PR-3 with a very competitive niche. However, the traffic is not there yet. That's why PR means absolutely nothing in my opinion.
Everybody is asking how to do it??? No secrets there: get: 1 PR 6 or 4 PR 5 or 20 PR 4 or 100 PR 3 or 600 PR 2 or about 3000 PR 1 links. That's all folks, no secrets at all.
I think it is really a mystery. My new domain also gets PR4, including 80% of the inner pages (there are 6-7 inner pages I guess). ANother 6 yo domain I bought has PR4 came with it. The PR didn't drop during the PR update. What is surprising is that most of the blog posts (5 or 6 of them) also get PR, ranging from PR 2-3. I didn't realize this until someone contacted me to advertise on my 6-yo site. How can this happen? Is this because of the domain age and reputation? I didn't write top quality posts there. The 5 or 6 posts were in fact the only I wrote from Jan'10 - Apr'10.
wow, congratulations! that is great, what was the winning formula? or you have no idea what actually worked. share the good fortune with all of us.
the OP didn't state how he got his pr to a 4 did he? there's so many ways to do this. someone asked if he used a bh method...possibly...scraping, cloaking etc...would be interesting to know how HE did it.