To me, McGuinty has pretty much been as good of a Premier as you would want. If he can survive the health care premiums then he can easily survive the HST. People need to start realizing that taxes can be good rather than automatically evil.
In terms of planning related issues, I agree with unimagintive2. On transportation and municipal issues, this government has been great. And as much as the Smart Growth plan was initiated in 2001, the greenbelt plan has this government's fingerprints all over it, and it could be something we're thankful for in 50 years from now.
For me personally, if not for Mcguinty's work on the post-secondary education front, I probably would have struggled to financially get through my undergrad. After the education mess that Harris left, he cleaned it up fairly nicely.