Maul was definitely a favorite of mine and a pity he was wasted at the end of TPM. But his role was to reveal the Sith and was more muscle than the brain that Palpatine was, so losing him was no big deal to the endgame. Recruiting Dooku to be the charismatic leader of the Separatists while scheming with Palpatine/Sidious on the Republic side was quite interesting. I was disappointed that Dooku had such a small role in the movies (introduced late on Geonosis in AotC and then killed in the Battle of Coruscant very early in the movie). I know the character was developed more in books or Clone Wars, but I just wish he would have lasted a little move into Sith... maybe they could have eliminated Grievous' role all together? Grievous didn't impress me.