i have used it in a shop, and its good stuff, believe it or not. i would have no problem using it on my car, in fact i have. PPG, Dupont, Sherwin-Williams (exact same as M-S with different labels), R-M, Glasurit, and Sikkens all have quality automotive paints. the best IMO would be Glasurit, but it is expensive.
(I did not include house of kolors in there, because nobody uses that in a production shop.)
edit: wait...cross fire? never heard of that line of M-S paints, but it has been about 2 years since i have used any M-S paint.
My wife's Corvette was painted with M-S paint in '87 and still looks great. It was the first time I've ever taken care of a car painted with bc/cc and made me a believer in that systems durabilty.
my folks used to own a hardware store and the paint they sold there was Martin-Senour and it was the best house paint i've ever used. i've never personally used the M-S brand automotive paint but have seen many cars painted with it and it looked good. my car is painted with sherwin williams so if it's true that the S-W and M-S paints are the same then i guess i do have experience with it. the S-W on my car is beautiful and is holding very well, especially considering the car sits outside and was painted almost 2 years ago. i like it very much.
i've used the crossfire system numerous times, and have found no problems with it. as with all painting, prep is the key to a good paint job. i use the generic basecoat (~21.00 a quart), and cc5000 for the clear. they are expanding their product line, and are offering many new clears, primers, and sealers. overall, great product at a great price!