Shin : I'm 16 years old. None of the coaches I've met in my life who could've played in the 50s have ever advocated a continental grip -- in fact, the one possibility of someone who's 60+ and coached, strongly stood against my use of the continental (I used it for a few months, during last summer and earlier this year). For that matter, even the most famous continental-gripper I can name, John McEnroe, isn't old enough to have been playing in the 50s.
The continental grip is a fantastic grip for a flat-hitting, placement oriented ballstriker whose main focus is to end the point, or get to the net. I found while playing with the continental grip that there were no silly mistakes. I never mishit the ball unless I was swinging wildly, and I rarely missed my mark. The problem is, it's not a very agressive or stable stroke, in a rally-type situation. For hitting a short combo of shots (say, deep to the backhand and then smacking away an inside-in winner) that relies on power as well as placement, a skilled player with the continental grip can rule the world; the ball moves faster (less energy is lost in the bounce on spin, and the lack of heavy spin generally rewards in deeper balls, also helping to make the ball seem 'faster') and the risks are not any higher. However, for someone who is inaccurate, or looking to spin their ball in (I assure you, you don't need all that much spin to hit hard. It's just more difficult, and you don't get much net clearance) the continental grip is horrible. I'm sure I could go on for days about the costs and benefits of extremely mild forehand grips (Continental and Australian) but it would also take days to format properly, and keep on point.