Brent writes:  "The GADAHRS is a component in a system, and how the system works is what is important. The system integrators, D2, are the ones with the answers to the relevant questions."

You mean like the answers they had when they were selling the 425EX?  As far as I know, no one at Direct To is a double E or has experience designing avionics or is otherwise qualified to evaluate a critical avionics component such as an AHRS.  I don't fault them for that; they serve a useful purpose and opened up a new market in affordable glass.  I know them personally and like them.  On the other hand, I would feel a bit foolhardy trusting my life and my wife's life to a critical product that, if it works at all, pushes the edge of technological feasibility and that is made by a group of people whom no one knows and who are not available to answer questions about their product, who publish no track record or other list of qualifications, who are apparently recently formed and whose product seems not to have had any exensive use in actual customer aircraft, all on the strength solely of some five word otherwise unsubstantiated claim that the product meets some tech spec and the word of a "systems integrator" who is, at least from what I know, not in a position to pass informed judgment on the product.

As I said before, I REALLY hope the product works but I would need to get a lot more comfortable about it and who makes it and how it was tested before I went into the soup with it for the same reason that -- yes, Brent -- I am heeding the service letter despite having had no problems with my 420.

When I bought my TruTrak autopilot, TruTrak was also a startup company.  The difference was that everyone knew who was behind it and what his track record was.  In the beginning, it had a number of glitches but, when you called TruTrak, as often as not, you got the Man himself.  You also got same day service on whatever the problem was so I was able to get fixes done with the system down for only three days.  Now that's a class act!