I feel underqualified for this poll... I just finished reading No Man's Land (am reading modern batman in chronological).
It is a shame, it is hard to get enough stories with Grayson or Todd as Robin, there is plenty stuff with Drake.
It was actually kinda weird, cause reading it in trades it felt like Batman recruited Grayson as Robin, but did not really use him, than Batgirl came along and robbed the spotlight, then suddenly Batman and Robin had their falling out, so Todd came along, but like in the next trade Joker kills him, and Drake shows up...
It feels like the first Robin was a long time partner, but I did not get to see to many of his missions, while Todd was almost non-existing. I am excited for the next change.
No that I dislike Drake... but these kinda role-changes are always exciting to have and to read about.