It would definitely be less hassle to get into the parks than a paper ticket. After getting my bag inspected, I have to pull out my keys (which have ID/card holder attached), get out my ticket sleeve, pull out the ticket, put it through the machine, and then put everything back together. With a wristband I'm assuming you'd just touch the band to a sensor, do the fingerprint, and be on your way. Is it a huge hassle to use a paper ticket? No, but this would definitely be quicker. I agree that I probably wouldn't want to wear it all day, though. It would be nice if it were adjustable/had connecting ends; then I could loop it around the strap of my bag.
I'm not sure how I feel about the reservation aspect of FP+ (and I'm not even sure how it would work for passholders/those not booking vacation packages), but it would be pretty nice not to have a paper FP ticket to keep up with. Oh, and no more problems with your ticket becoming demagnetized and not working at the gate or FP machine, either!!