Let's say everyone that searches on your favorite keywords knows about, and uses, the 5 major web sites that attract 98% of the traffic to them...and you are not one of them. Would it make sense to include links to those sites (even if you view them as competitors) with the keywords in the link text, as a way of gaining visibility in the SERPs?
Back in Nov. around Florida time - I added some "themed" outbound links to dominant sites in my category - with all of the changes on google all the time --- its hard to say 100% --- but I "feel" that this does help
By linking to sites that are unlikely to link back to you, you are reducing the proportion of the your reciprocal links to your total outbound links. I don't know if Google takes this into acount but I have a gut feeling it does.
I have experienced a surge in PR when I put a number of outbound links on a page. Perhaps it coincided with other factors that caused the improvement, but I am, for the moment, going with the "outbound links help" approach. Oh, and for the sake of staying on topic, these sites that I linked to were not major players but were just your garden variety sites.