The formula and weighting is different than FICO. It doesn't mean it's worthless. Remember the lenders do not for the most part use the scores you pay for at this site either.
Actually, the scores from this site ARE used by the majority of mortgage lenders. Fair Isaac is on record as saying when the majority of mortgage lenders switch to their newer version then this site will begin offering their newer version. It is true that we cannot pull some other scores such as the "Auto-Enhanced" variant, but what we pull here is indeed what most mortgage lenders use.
As you said not for CC or car loans.How many mortgages does anyone apply for in a lifetime? In addition to your score there are many other factors that determine your rate as well.So while it may be helpful for some to know their scores( tough to know your middle score now though isn't it?) it is only one piece of the puzzle.