I bought my 3 inch M-547 NIB in April, 1983. A local sporting goods store had them on sale and I paid $284.45 for mine, including about a 6.5% sales tax.
I shot it a fair amount at first. I got some HKS speed loaders for it but never used it for anything but plinking. It shot well with everything I tried in it. I had briefly, before this, owned a 9mm Ruger Speed-Six (I think it was) that used a stretched coil spring around the ejector star to extract cases, but the last one or two rounds were hard to insert and they didn't always empty after shooting them, either. The S&W arrangement was a far superior if somewhat more complex system to shoot the 'rimless' autopistol cartridges.
A fellow I used to run into at a local range saw mine the first time I shot it and ran down to the same store and bought their last 4 incher. The guy was a huge 9mm fan and brought 9mm reloads and milsurp ammo to the range by the bucket-full. I ran into him a few times a year for quite a while, and he always had the M-547 and a very pretty, engraved Browning High Power with him. It was common for him to fire 500 rounds or more in an afternoon. We kept waiting for the ejector mechanism of the revolver to fail, but it never did. He had fired thousands of rounds through the S&W by the last time I saw him.
One day he had some imported, high pressure 9mm mil surplus ammo he said had been sold as suited for blow-back operated submachineguns, not handguns. He shot some in an old Star B, and it kicked quite hard. He then shot 6 rounds in the M-547. He said it kicked as hard as a Model 19 loaded with Magnum ammo, if not harder. Then he tried to eject the brass. It wouldn't. He tried pushing the ejector rod against the bench top. Nada. He finally borrowed a hard plastic mallet from another shooter and began to beat the rod back! The fingers of the ejector tore through the brass cartridge case rims without moving them! The primers were as flat as any I had ever seen in a handgun. Those cases were stuck!
He told me that he later took the cylinder out of the revolver at home and soaked it in penetrating oil, then drilled a hole in a block of hardwood and used a brass punch and hammer to drive each spent case from each chamber, using the block as a sort of anvil.
That ejector system is pretty rugged!
S&W had discontinued the Model 25-2 1955 Target in .45 ACP by then. When I saw the new Model 547, with the unique ejector and extra "limit pin" (what the second 'firing pin' is called), and how well it worked, I thought, and hoped, that S&W might use this new system for their next series of .45 ACP revolvers, instead of moon clips. I was slightly disappointed when the Model 625-2 was introduced with a conventional moon clip-based ammo extraction system.
I bet that the Model 547 was one batch of handguns that S&W made no money on. The development of the system and the extra manufacturing steps needed over the same gun in a conventional revolver round must have been expensive.
Dick Metcalf was a writer for SHOOTING TIMES magazine in the 1970's and 1980's. He wrote the evaluation article for the then-new Model 547 and was very complementary about the new sixgun. He was impressed with the accuracy he got from his sample and wrote about perhaps adding a S&W click-adjustable "Target" rear sight assembly to his, to wring a bit more precision from his. I don't remember reading if he ever did.
Undoubtedly, the Model 547 9mm M&P is one of the most interesting revolver variations that Smith & Wesson has ever manufactured.