Given that events were going to unfold the way they did, this was I think the best way for it to happen. At least now there won't be Iggy vs. Rae surrogates fighting for the "interim" position in an unseemly fashion.
The main event is going to be ugly enough. Why be forced to endure the warm-ups?
Update: Count me as being one of these guys:
Some Liberals privately suspect Dion decided to stay until his successor is chosen in part because he wanted to avoid a power struggle between the Rae and Ignatieff camps over who would be interim leader.