Jonathan -- thanks very much for your comments and guidance. You have helped me out and provided advice on other issues and postings on the forum and it is greatly appreciated.
(1) FYI, the Mack warranty extends the US warranty on US products. They also provide the only coverage provided by B&H for grey market products.
I also was independently referred to the following review of repair facilities on Photo Net which is very educational:
http://www.photo.net/neighbor/one-subcategory?id=1All of these comments persuaded me to skip the Mack warranty. I'll hope and assume that any problems that may develop will occur in the first year under the Canon warranty. (Which is generally the case -- and why extended warranties are a bad investment.) If problems occur after it expires I'll just send the camera directly to Canon and pay for their repair services. Better to pay and hopefully get the job done correctly the first time.
The reviews on Photo Net were very educational. The comments about Mack range from "a monkey can do better" to "worthless, absolutely worthless." It appears to take Mack two, three or four times to get the job done correctly, assuming that they get it done at all. You can also read responses from Mack and B&H -- you can read both sides and decide for yourself. My conclusion is that there are very few positive comments about Mack in any of the forums.
This only confirms my earlier stated view of extended warranties. I should have known better than to have wasted even a nanosecond considering an extended warranty -- especially is it was not offered directly by Canon in the first place.
(2) With regard to my comment about the "relatively large number of problems" reported with the 1Ds. That was an unscientific statement on my part -- I readily concede that I would be hard-pressed to defend it. I base it upon comments posted in the Galbraith forum where a fair number of problems have been reported. I have already had such an intermittent problem with my 1Ds -- time will tell if it is serious and needs to be repaired. My impression, again it is only an impression, is that there are a larger number of problems being reported than normal -- or what you'd expect for a professional camera in this price range.