I think this question has become much more complicated than it would have been, say, ten years ago. Back then, a computer was a computer--what we consider a "desktop," "laptop," whatever.
Nowadays, so many people carry computers around in their pockets, in the form of smartphones. If I had to take a stab at my "traditional" computer usage, I would say it's a fair amount...mostly because I use it as my main source of entertainment (it's how I watch DVDs, and my stereo system is entirely computer-based on the digital end of things). However, I've owned a smartphone for over a year, and I'd say I check it on probably an hourly basis, and I use it frequently for podcasts and for reading the news (I get the Sunday New York Times, but that's only once a week...not exactly the best for staying current!).
All told, it's impossible for me to calculate, if you include smartphone usage. But I'd say it's quite a fair bit more than it was a few years ago!