Thank you for providing productive procrastination for me so I can get a break from the monotony that is constitutional law >_>
What's it actually like? Does it offer any interest for a mind that prefers creativity and dynamicism to routine?
I guess so. There's rarely any right answers in a law exam. Most law exams consist of the description of situation, followed by questions like "Advise A as to his legal rights (if any) in relation to <legal principle>".
I guess if you wanted to be creative, you could take an unorthodox view (though some lecturers might not like that), as long as you can defend your answer with statute, legal precedent and to an extent, academic commentary.
There's also policy questions on most exams, which basically ask you to critique an area of the law. So you can really get into giving your own opinions and interpretations of the law there.
If you mean creativity as in theatre/music/art then I can't help you

As for dynamicism, well, the law changes very often... umm... Well, each law subject will have its own idiosyncrasies, although there are of course a common set of principles applicable to all areas of the law. But I would think that were the case for most disciplines.
Do you have to defend clients who you hate?
I'm not sure, I think as a barrister the court can order you to defend a client. I don't know what the rules are but I have a feeling that if you really hate your client, you could argue that you are unable to act in his/her best interests and therefore you cannot act as their lawyer.