I know for a long time that the best backlinks are one-way backlinks, however, I've been noticing there are a lot of really high pr websites are very active in link exchanges, as a result, even though their websites got thousands of outbound links, their pr survive updates! So, here is my thought: link exchange may not help your ranking (SERPs), but it still help your pr provide that all links you got are do follow links. Do you think it is correct? Please share your opinions.
Link exchange are helpful if the site was related to your niche. But not give high value as one way link from related site. Link exchange will work if link page is cached, sufficient text related to your link and not having more than 20 partner links. Link exchange is good . It depending upon the partner you have linked with them.
Instead using just a regular 2 ways link, you should ask your link partners to do 3 ways link.
However, only exchange links is not enough to boost your site's PR, you need to look for another
inbound links source for your site in combination.
Dofollow one way related links can boost your PR without a problem but shouldn't over do it. There should be backlinks from nofollow sites as well as from none related sites. That way Google won't ban your site from their search engine for trying to manipulate the search result.