I think the charges and counter-charges regarding Kerry's and Bush's military records are ridiculous on both sides.
Looking at Kerry's FITREPS on his own site, it is clear he was a competent junior officer.
As to Bush not going to Vietnam - recall that peak US deployment in Vietnam was roughly 550,000 out of roughly 3,000,000 active duty forces. US forces were deployed elsewhere in the world (e.g. 300,000 in Germany at the time), and it is unexceptional that a veteran of the Vietnam era would never have been in Vietnam. Especially an F-102 pilot, which was a bomber interceptor unsuited for operations in Vietnam.