Hello all, I have a blog that has been running for a year but still in /?p=123 format which is not SEO friendly but has a PR3. Can advise me if I should change my perma links to /%category%/%postname%/ format at this point of time? What is the risk level? Is there any wordpress plug-in to recommend me? I am currently running wordpress 2.6.1.
If you change you'll lose any link juice to the old URLs. You should do a 301 redirect from the old URLs to the new ones if you change them.
My Dear Brothers and Sisters Its always good to have static url instead of dynamic and try to keep it short. Secondly whenever you do redirect of old url do it 301 permanent redirect otherwise it be considered as new url and you want get PR and backlinks of your old URL.
Providing the redirects are proper 301's, it will be fine. I use Scott Yang's Permalink Redirect. Works fine under 2.6 so should be good for 2.6.1 http://scott.yang.id.au/2008/07/permanent-redirect-20-released/
you'd better keep the old ones for several months, when you post many new posts with new contents for several months, you can have a try to let all the old ones jump to certain page.