I have wanted a Model 18 for thirty or so years, but never saw one at a reasonable price.
I just traded for a 10 shot 617, and after 200 or so rounds I am very pleased with it. The cautions about timing, feel, and not being able to lighten the mainspring were all groundless, at least on mine.
I have the 4" version.
It seems accurate, and it is a lot of fun to shoot D/A.