madoctopus started another thread which I think compliments the info in this thread as well.
He has diagrams and charts explaining how powerful backlinks are worth depending on the PR of the pages you get them from. I think the charts apply to this thread as well so I'm quoting them here. I don't know how accurate the charts are, but they give a good idea of the comparison between links from pages of various PR levels.
If you like these charts be sure to check out his thread and leave him some thanks.
PageRank Illustration - Now You Know Why It's So Hard
Here's one of the charts:
Here's the other one:When looking at these charts, remember what was said earlier. This isn't about increasing the PR of your pages, the value is in the power those high PR pages give to the backlinks you get from them.
Check out that second chart. One backlink on a PR2 page is the same as getting 101 backlinks on PR1 pages. Even more impressive, one backlink on a PR4 site is the same as getting 3044 backlinks on PR1 pages. That doesn't mean getting backlinks on PR0-PR1 sites is bad, just that the higher the PR of a page the more valuable a backlink on that page will be for your site.
The only problem is it's not always easy to get backlinks on a lot of high PR sites. That's why it's still good to get backlinks on PR0-PR1 sites. Since those comprise the bulk of all pages on the internet, the PR0-PR1 sites are also easier to find and get backlinks from.