Re: engineers good, systems bad
See http://aaisp.net.uk/kb-broadband-sfi.html and http://aaisp.net.uk/kb-broadband-sfi-isp.html for the view from an ISP on the 'old' SFI product.
This has now been improved somewhat with SFI2 (http://www.openreach.co.uk/orpg/home/products/serviceproducts/sfi2/sfi2.do), but still ain't great.