I think they are a good sturdy revolver. I would prefer something else, but would expect them to fire reliably if provided with good ammo.
I believe the cylinder is only locked when the trigger is held back, so the cylinders can turn freely at other times, but probably would not turn in a holster. Not a huge problem, but nice to know. A lot of guys like to carry differing loads in a revolver out on the farm (a few snake shot loads for close in snakes, a few hollow points, maybe a hard cast solid or two at the end); if the cylinder did its own thing without consulting you, you might be unhappy when you found out.
I question the effectiveness of the ammo as compared to 9mm, 40 S&W, etc. But compared to being unarmed, it is pretty effective after all.
When these first got dumped into our (US) civilian arms market, they were selling as low as $49 at times. Then they crept up but are back down in price, I think due to more imports. I'd expect them to go back up in price if the importation dries up (whether due to admin reasons or supply drying up).
A good S&W 38 special would be a better bet, and can be found for $250ish if you look carefully, depending on where you live and all that. For under $100, not much else beats a 1895 Nagant revolver.