For the recreational sailor who likes to sail in heavy wind, what has been your experience with this anti-pitch device? Do it change the handling any or does it just seem to raise the bow out of any waves or water it goes into?
Does it prevent all pitchpoles?
It doesn't prevent pitchpoling. No little foil is going to stop you from going over when the leeward hull goes under. In fact, the first pitchpole I did doing a jybe showed me how, of course, not to jybe in 40kt winds, but how when the wind has enough leverage to lift your boat out of the water, it will flip you on the tip of the bow, not submerge the entire hull, and the water grabs the foil and may do more harm than good.
That being said, I still have my foils on. 
Jason
There are many that swear by them... They will keep the bows from driving under in NORMAL conditions. But, certainly not the 40kt example above.
I used the foils on my H16 and thought that they allowed me to push the boat a little harder without the constant worry of a violent pitchpole. I still respected the fact that they weren't going to stop a PP under the right conditions.
Jack
What is the device made of, is it plastic or metal?
Metal.
I drove my leeward hull 6 inches below the waterline on a reach for a long duration. I don't know if the foils prevented the pitchpole, but they probably did. I don't wear them anymore though.
Greg H14, H16