Well like everyone else, I was not sure that it would make the difference that it is suggested to.
When I received it, the thing felt alien to my hands at first, but listening to other reviewers I persevered and I got used to it-COMPLETELY used to it. So much so that now I don't like the feeling of the controller without it.
First of all, it really does space out your hands, and my hands no longer feel quite as arthritic as they would previously...actually a long way from it, so in that respect it does it's job well.
Second of all, the 'air channels' if you can call them that, technically must work, but because of the synthetic material that the xtendplay is made from, it counteracts this and probably makes your hands sweat more than the standard hard plastic of the controller. I am lucky that my hands don't usually sweat, but I think this will vary from person to person.
Third of all, the length of it makes it extremely comfortable to use as it can rest on my lower stomache, with next to no pressure or weight and therefore relaxing my arms a lot. This would have warranted 5 stars by this point, however...
...for some reason when using a wireless controller, it has a problem with encouraging the controller to disconnect-OFTEN. At first I thought this was due to batteries, so I changed them. Still happened. Then I changed the controller to a different one all together. Still happened. I then changed those batteries-guess what? Still happened. Once I hard wired the controller, the problem no longer existed, which leads me to conclude that inside the controller itself, wherever the wireless antenna sits, must be getting the signal blocked by the xtendplay. This is generally supported by the fact that most of the video footage I have seen of the xtendplay was utilized using wired controllers. This is an annoyance, hence the lost star.
All in all, it's worth the money, and I would encourage any gamer who likes to have full day sessions to pick one up. And if anyone is wondering if there is a barrier created actually playing the games using this unit, then rest assured there is not. I have been playing Deus Ex: Human Revolution, Mortal Kombat and Gears Of War 3 recently with the xtendplay, and in no way does the controller get in the way.
Just get it.