I had always imagined that becoming an animagus would be difficult in the way casting a patronus or resisting the Imperius curse is difficult: something that requires extreme mental concentration and willpower. Instead, the recently-revealed process seems tedious, easy to mess up, and mostly dependent on luck. I’m not sure I like it.
I have to admit, I’m not sure I’d be able to keep a leaf in my mouth for a month straight. I’d probably chew it up and swallow it the first time I ate something, or spit it out without even thinking about it. And waking up at sunrise to perform a spell every day would not be fun, because I’m really not a morning person. But those are both mundane challenges compared to what we normally see in advanced Harry Potter magic. Having a clear sky on the night of the full moon and a thunderstorm as soon as possible afterwards is just a matter of luck.
Only the last step – the actual transformation – seems “magical” (as in, not just a complicated and tedious list of instructions). And there, it seems as if – as long as you did the other parts right – there’s very little that could go wrong. The danger of messing it up comes when you’re carrying around a mandrake leaf in your mouth, casting the same spell at sunrise and sunset every day, and keeping the potion hidden until the next thunderstorm.
I can see why so few wizards ever decide to become animagi. Especially when the risks are so high: becoming a “horrible half-human, half-animal mutation” is an awful thought, especially since there is no cure. And you don’t get any say in what animal you’re turning into, so wouldn’t it be awful to waste months or years trying only to find out your animagus form is a rat or an insect?
On a different note, the potion used to become an animagus has to be set out in the full moon, which makes me wonder if there’s some connection to werewolves. Was the first werewolf actually trying to become an animagus, but the process went wrong so that instead of keeping his mind and transforming when he chose, he was forced to become a monster once a month? I don’t know if it’s what J.K. Rowling had in mind, but I like the idea …