I have the compass mostly for nostalgia, it puts a little "Bear" in my bow. Like others have said a hand-held and map are the most dependable and a GPS great as long as batteries and satellite views are ample.
However, I think of three times in my bowhunting life when a compass in the riser would have been useful. All three times, twice in Colorado and once in an Indiana cornfield, this little compass would have provided some comfort and maybe saved me a few anxious moments.
Both the Colorado instances involved me going just a short distance and I decided to leave my fanny and its enclosed compass at camp and with a dead bull. I was only going a couple of hundred yards. Both times I spent about an hour before I could get my bearings and find my way back.
Again though, if you don't prefer the look (like I do), I wouldn't have one installed, there are other more efficient solultions to navigation. I have three more of the little jewels that will one day find a home in other risers.