Tending not to use them presently. For me it depends on which site. Some niches tend to explain themselves very well as is, and an about page looks extraneous. Especially with more unique or unusual niches, I feel a need to explain a little more in the "About" page, to inform and get readers excited about the topic and site.

I'm not ready to take on very personal thing in an "About" page because my focus is more on what the site has to offer others personally.

An "About" page also gives me another place to provide text links to sponsors. I try to do them carefully here so they're relative/useful/interesting rather than blatant, forceful pitches. Same with any banners if they work at all here.