Yeah, it really depends on the other candidates running. I have been disappointed by Miller and what really hit it home was his childish fit he took in 2007 after the delay on the new taxes by closing libraries on Sundays (except in those oh-so-special "priority neighbourhoods") and raising TTC fares while delaying by a year the needed service improvements.
I know that Miller has meant well, and has been a big leap over the lunacy of the Lastman era (the first year or two were exciting) and there's been more festivals and that and some positive developments. Perhaps the expectations were too high.
I should say that all the "Socialist/Communist" or "Tax-and-spend Miller" like comments are just weak right-wing snipes. There has been little in the way of thought out, constructive, or reasoned opposition. I think that's a lot of Toronto's problems. A good, strong and diligent opposition is essential in a democracy. Not Royson James calling for lynchings or Rob Ford blowing gaskets. That's weak and lazy.
Trouble is that most of the potential candidates are jokes or not serious, like Ford, Stintz (though she's mellowed) or David Peacut. Smitherman would be worth watching, but I have heard he is difficult to work for/under and can be very abrasive. There's Royson James' pet candidate, Mike Clemons, but while a nice guy and all, shouldn't be a serious candidate. I have said before, Clemons could make a good Lieutenant-Governor, but not a Mayor. Michael Thompson could be an interesting candidate - apart from one early, but huge gaffe, he's been a relatively level-headed centre-right who's matured politically. If not 2010, then 2014.