Physics GRE Discussion Forums

I hear that how well known your advisors/recommenders plays a big factor when applying for PhD and the life after the PhD with said prof.
But what counts as a well-known or famous professor? I am asking because I want to do a PhD with a professor at University of Hawaii who I know personally and I like him a lot, but I have a good enough resume to get into a top 40-30 University.
Maybe his reputation would counter the not-so-stellar reputation of UHM?

I want to do a PhD with a professor at University of Hawaii who I know personally and I like him a lot

The most important thing when getting a postdoc is publication history. If you and this prof work well together, then it shouldn't matter the reputation of him or the school; you should go work for him. Making decisions like these will make your PhD infinitely more enjoyable, and if you have a good relationship with your advisor it will be much easier to get papers out anyway.

The best bet is to figure out where their former students went. This usually comes to water cooler gossip type conversations with other students (though I suppose it shouldn't be impolite to ask a potential advisor where their students went).

EDIT: I'll add that I've heard stories of very famous professors getting their former students subpar postdocs.