I remember when I was just a wee lad playing Gold and Silver, embarrassed to say thats when I really got into the games. (I do love RBandY though, for reference) I used to use the master ball on the first legendary I came into contact with, which happened to be Ho-Oh. And when I got to the legendary birds or dogs, I was soooo mad that I didnt have another to catch it with. That was just a little history.
Now that Ive gotten older and more experienced in the games, lol, I try my best not to use the Master Ball unless I absolutely have to. Currently, having just finished Black 2, I have Latios, Terrakion, Virizion, and....wow..cant remember the last one. But you get it. I still have the Master Ball and I dont plan on using it...hopefully. Oh and the same case with Black, figured I shoulda referenced that in here seeing as its in this thread :)