I just replaced the IO550G. I did the reman because the plane was damaged during Sandy and the engine required a teardown. It had about 1500 hrs on it. Financially the cost of the teardown was a little more than the value of the remaining time on the engine, plus the insurance paid for the R & R. I decided for the same money to fly behind a new engine and have a newer engine when it came time to sell the plane.
The biggest cost to upgrade to 310 hp with the 2700 RPM limit is the new propellor. If the prop had been damaged I probably would have done it, as the insurance would have had to pay for a new prop. Alas, no prop damage. I think the upgrade is worth it, but it's about 18K with the STC, new prop and labor. More than I care to spend at this point. I think the 2 blade prop is a little more efficient, but the 3 blade climbs better. Probably not much difference.
I agree that they should have just replaced the mounts while the engine was out. I was PO'd at the mechanic that he didn't.
I also asked him about the hoses. He said all the fluid carrying hoses come new with the engine from TCM. He did not replace the transducer lines, again saying they were "on condition". I'm less PO'd about that, but I just don't understand why he wouldn't offer me the "kitchen sink" firewall forward treatment. Maybe most of his customers are stingier than me, but at least let me make the choice.