Long lens support

HERE IS THE PRODUCT

So I stumbled upon this gadget on the RRS site.

I made a nice sale yesterday and think it may be time to put the 500/4.0L IS in my arsenal. I have, over the years seen a few people shooting on home made versions of this. I just want to ask the masses if they think it has a real life benefit on the quality of images (especially with IS). If I was not so very in love with shooting slow shutter speeds I would not even consider it; but alas I am.

The image is not mine it is from the RSS page that I have linked to, all the information is there too.

Send in your thoughts.