From my point of view as equipment sales staffer. I can honestly say I have to agree with comments made here. Typical retailer (and customer when I am speaking on behalf of one) recently has been absolutely hopeless from Canon. Long winded, uninformed....I feel Sigma aren't far behind in those poor stakes either.
Whilst, my experiences of retailer support in two separate retailers I've worked for has been moderate with Sony (We presume that over priced Sony Centre's do need some sort of lift against high street opposition!?). Support from both Nikon, JVC and believe it or not Kodak, really has been second to none
However, with the exception of a few models...(example quite recently the unfortunate high profile problems with Canon 1D mkIII).....generally speaking what you get is what you pay for. I might well be a bit of a nikonian at heart(and always have been really), but I have to admit the new 450D and 40D units are exceptional cameras......just so long as you don't have one under manufacturers warranty with an intermittant problem (If judging from the poor service they've provided to some of our customers of the 400D)
...That isn't to say we haven't had one or two Nikon D40's back tho!
Horses for courses I suppose