Everyone's mileage varies, but I've used a CD-Rom (or DVD) maybe 3 or 4 times in the last year, despite being a computer professional.

I do find I use USB sticks somewhat frequently and portable USB hard drives daily.

Lots of my co-workers freak out at the idea of not having a CD-Rom drive so I've always had a USB one in my desk but just realized recently when I stumbled across it that I can't remember the last time I used it.