There is studies...
Looks like the studies were redundant
My cell phone is still very much just helpful. I'm on call at work, but that's changing soon, and I'd have a pager if I didn't have a cell phone, so it's not any worse. If I don't want to be bothered once I'm no longer on call, I can always turn off my cell phone.
This is a big part of the reason I don't want a Blackberry/Treo/etc. I want my phone to stay simple so it remains just a useful tool and not too much of a lifestyle change.