You should pay no attention to toolbar PR when you’re exchanging links. It’s only a snapshot of an estimate from an undefined period of time ago anyway, so it represents very little.
You should be more concerned with whether or not you’re linking to a good quality site that your users will find useful. Recommending good sites makes you a resource. People bookmark resources and return to them. You should link to great websites and pages regardless of whether or not they give you a link back. If every link out from your website is a reciprocal link, what kind of message does that send to the search engine?
You should also think about co-citation. Is your link on a page with links to other quality websites? Or do they link to anyone who is willing to link back?
Having your link on a page that links out to a bunch of rubbish sends a signal to the search engines, and I’m not sure it’s the image you want to send.
Every page had a toolbar PageRank of 0 when it first launched, even the PR 10 pages.
All of the above is just my opinion though, for whatever it’s worth. 