I am thinking of getting one to put on my 16" varmint upper. Hoping to find out if any one has put one on and if they liked it or not. Also how hard are they to put on? I have never had a free floated upper before and have not taken it apart yet.

I have one and like it well enough.  They are no different to put on than any other 2-piece float tube.  Requires the removal of the barrel and front sight.

I have one that I put on a lightweight gun I was building. I would post a picture of it but webphotos is down! I like it very much for what it is. It keeps the weight down and free floats the barrel which is what I wanted. They do look very nice as well. I am sorry, but I cant tell you about putting it on. A had a friend who is far more competent than I at such things do that for me. He did not mention it being at all difficult, but he knows what he is doing.

Crane center like it enough they used it on their SPR-A(Special Purpose rifle-A).  You can do a search on SPR and you can see some cool pictures.  

Precision Reflex is company that produce the handguards for them.