I do!
I fly as a glorified taxi driver in Sunny England. I wear mine mostly out of habit. I find it handy because you never know when you might want to jot something down. Normally just thinks like T/O time just before I lift, or landing time, what fuel I bought where, etc...
My map never lives on it but I do find it useful to clip my map/airfield map on for cross country or unfamiliar airfield stuff, it just keeps another hand free.
Moral of the story; I never know when I'm going to use, sometimes it doesn't even get used. But it can free up a hand, normally when your trying to think about serveral things at once.
What to look for? Biggest thing for me in a helo, would be one that isn't too wide. Most plank ones are pretty fat. If you have high collective and need to apply back/left cyclic it can get in the way (which is not useful!!!). Apart from that, make sure the pen holder is on the side not along the top because it makes it a pain in the ... to clip anything onto it with one hand.
Hope thats useful