Buying expired domains for PR, does it still work?

I’ve done some experiments over the past few months about expiring domains with PR to see if it is worth your while to catch these expired and deleted domains. My idea why I would like to use expired domains is the notion that old domains are favored than new domains, and to get instant PR. So I set out to find deleted domains with PR that I can register. One characteristic of domains I was looking for was that the domain still had a PR, and it was still listed in google. I won’t be mentioning the actual domains here as I need to control the results and prevent people from making backlinks to these domains. I registered about 4 domains, some have PR2 and PR3. Some have a few pages indexed, some have a few thousand. I also bought a couple of new domains for my new projects. I found out that google rarely visits these domains so I need to prime it but with some fresh backlinks. After creating some backlinks to these domains, two domains eventually lost their PR. These two domains have only a few pages indexed in google. In one domain, I did a 301 permanent redirect to the new index page. This domain retained its PR. One key difference this domain has compared to the other two is that this domain has thousands of pages indexed in google. In another domain, I did a 301 and redirect it to a fresh new domain. The result is that the new domain got indexed faster and more pages were indexed compared to another new domain I registered at the same time. However, PR was down to 0. There is also a case where I did a 301 redirect from an old deleted domain with PR and never got any benefit from it. In conclusion, there is still conflicting results on whether buying deleted/expired domains. Some works, some don’t. However, what seem to work is that… a. Old delete domains does contain traffic from existing backlinks. If the old domain has tons of backlinks, it still does generate some traffic. b. Other search engines such as yahoo and msn do not seem to have an biases against expired/deleted domains.