My son started out as a LH hitter but, by the age of 8, he had already started dabbling at switch-hitting. By about the age of 9 or 10, he was switch-hitting in every game. Frankly, at first I was very much against it because, starting from the LH side, he was already where most hitters would like to be. I heard of no one who started as a LH hitter who began to switch-hit.
However, he perservered, working on it largely by using a full-length mirror. He'd stand there for an hour at a time, watching his LH swing and then trying to duplicate it EXACTLY from the right side. Ultimately, He became very accomplished at it...in fact, I've not seen another player (in any of his age groups)do it as well (he's now a junior in HS). For years, now, his swings have been, quite literally, mirror-images of each other. Other kids I've seen who've SAID they're "switch hitters" seem to really mean that they're RH hitters who can bunt from the left side, or chop down enough on a ball from the left side to beat out an occasional infield hit. Personally, I don't consider that comparable or, in the long run, very worthwhile.
Down side: His hitting coach says it's literally twice as hard to become a proficient switch hitter. Just in practice, for example, if you'd ordinarily hit 100 balls off the tee in a practice session, as a switch hitter, you must hit 100 from EACH SIDE/EACH SESSION, or you've only done 1/2 as much practice as you'd have done hitting from just the one side...you can't get better that way. His point was, it's hard enough to develop AND MAINTAIN a good swing from ONE side, let alone, from BOTH sides.
Up side: I don't think this really showed up until he started regularly seeing good "breaking stuff." However, he now seems to have at least one important advantage over those who bat from only one side: The ability to stay locked and loaded in the batter's box. He will never be given to having his knees "buckle" on a late breaking ball that seems to break just over his elbow...on him, it will ALWAYS start outside, and it will ALWAYS break down and in. He can afford to just sit and wait on it.
Certainly, I'm no expert (unlike many on these boards), but it seems to me, if you're hitting .500 from one side or the other, like TR suggests, why mess with success? However, if you're a .270 hitter struggling with the breaking ball (particularly, getting "happy feet," where you find yourself tempted to "bail out") it may be worth a try. But, don't think it's going to be easy...