[@ImportantNobody] The DBZ transformations, sans the giant monkey probably, were about 95% positive. After practicing it(and really, most people aren't coming in with a transformation that's half cocked), they could change into it and maintain it, for a very long amount of time, effectively killing any drawback. But they essentially restored energy, and put them on a higher level of fighting. Goku was getting rocked by Frieza, until he went Super Saiyan, and that was basically the whole deal for every enemy. 

Anime is terrible for transformations really.