I have the current model 63-5 8-shots with 3" barrel. It's a very nice gun, feels great and balances well. I think 8 shots in a compact frame size is a good compromise. The finish is very good and tolerances are tight. The cylinder especially is beautifully machined and finished.
It has been 100% flawless and reliable with all ammo. I have not had even a hint of sticky ejection, and not had a light strike.
I have one nit-pick and a general complaint. The nit-pick is that the fiber optic front sight was not bright at all. I've seen pictures of the 63-5 where the front sight really pops, but mine was quite dull. Not a huge deal, and I can replace it or put a glob of glow paint on it.
The general complaint was the heavy DA trigger. It wasn't monstrous or anything but was pretty stiff. I know this is required for reliable rimfire ignition, but this is one of the few Smiths I own that is a candidate for a trigger job. I do realize as a hiking, trapping or plinking gun it will most often be used in single action, and the SA trigger is quite good. So I may just let the DA trigger smooth out on its own over the years.
I also own a very fine 6" K-22 which is notably more accurate in my hands than the 63-5. This is to be expected. If you want the best accuracy, the 617 will easily top the 63-5. The benefit of the J-frame is the size and weight.