[Milu]

I'm a management consultant, developing and implementing real world solutions is what I do for a living.

Conceptually sixsigma is a good package.

However, the way it is applied in industry is only valid for companies of a certain size, about 500+ employees. A lot of small businesses have been tricked into applying it by their large customers who use it. (level 1 suppliers in the auto industry to their level 3/4 suppliers for example). Many of the original proponents of it have abandonned it, sometimes in favour of a very reduced partial approach (8D) which covers the minimum requirement for their suppliers.

If you really start analysing it there is not really anything new in it. It's just the management fad of five years ago. Like business re-engineering was the one of ten years ago.
The selling point often used for Sixsigma is that it brings in measurable results. This would be more impressive if they were measurable on the bottom line in the annual accounts.

For what it's worth that is my humble opinion, more information is my professional opinion which is available for an exorbitant fee.