Krillin's transformation is mostly good, but the catch is really his speed. If you aren't used to being able to fly that quickly (almost twice as fast as Goku or Vegeta, and twice as fast as Gohan or Trunks), you wont really be able to use it. Personally when I transform with Krillin I spam scatter beam (which is this game's equivalent to an Ultimate Attack). The scatter beam is pretty much just 6 fully charged finishing busters that home on your opponents. No technique compares to it in power and speed, not to mention that you can't get stuck in a struggle with it and you can start charging another one right away. However, when it comes to melee, you have to know how to use that speed. I don't. I'm not better in melee with Goku, Vegeta, or Buu, than I am with Krillin. He's just way too fast for me, and the more speed you have, the easier it is to overshoot your opponent or make too wide of a turn while swooping. With 150 life transformed, and 300+ speed, he is undoubtably the greatest character after transformation, but you have to know how to take advantage of his power.