Whether John Mayer is cool or not doesn't bother me the way it seems to bother some music critics - I guess he's too popular to be really cool or something. Although he's had some pop-sounding radio hits and has received multiple Grammy Awards (and is nominated for more this year), what impresses me most (as a songwriter and as a listener) is the strength of his songwriting. His writing was already strong on his early albums, and it just keeps getting better, as do his arrangements. His guitar playing is also quite amazing, both acoustic and electric lead. He's a great live performer too (I've seen him in concert twice with my daughters).
This unsolicited endorsement was prompted by hearing Mayer's most recent album Continuum on my iPod while driving to work this morning. I hadn't heard most of it in a couple of months, and as with so much of Mayer's work, it sounds fresh every time I hear it. Popular music that's also really good is not that common these days, so I thought it was worth mentioning. John is also a blogger.