I think the real mark of a good club is that well-informed amateurs choose to play it. As an amateur, I have the freedom to choose the clubs I think are best, without having to compromise. Most professionals don't have that luxury, either because they need the sponsorship money or, for the top players, because there are deals on offer that are too good to refuse.
I really like the fact that Mizuno does not play the big name sponsorship game. They have proved that their reputation does not depend on the endorsement of the top players.
I think a lot of people, whatever clubs they play, see Mizuno as the keepers of the "true religion" when it comes to forged irons.
In the so-called game improvement category, I don't think people necessarily regard Mizuno's technology to be as good as that of Ping, Callaway, Taylormade etc. This is a shame, because there have recently been big comparative tests where the MX-200 (forged, but a "game improver") has come out on top.
This is where, perversely, a big name would possibly help. For example, lots of people may play Callaway because of Phil/Ernie or Nike because of Tiger, but they won't buy Tour Authentic Prototypes or the TW blades, they will buy a game improvement club. If Mizuno did have a major-winner endorsee, even it they played an MP iron, it would probably help sales of the MX-series clubs. The MX end of the market must be much bigger than the MP end, so it could be good business.
Deemac, I may have talked myself round to your point of view!