Sixty-5 guidance system. Any experiences?

I have been looking at this sytem:

http://www.ebay.co.uk/itm/Sixty-5-G...936183?hash=item1a186cd877:g:K-IAAOSweWVXdkXF

Has anyone used it? Is it any good?

My intended use is for grassland only spraying, fertiliser, mowing, rolling etc.

Cheers.