i generall prefer 'free' camera, for it allows way better reactions and control over your hero and units.
but the thing i would most like would be something like this:
you units each have a "change cam" button, that is a spellbook. Within there you can choose to go to the next unit, previous unit, next hero, ...
The cam is always looked onto the unit you have currently choose. But not totaly looked but more like "has to be in range X of choosen unit". so if you get to the border of these area, you'll be dragged with the unit, but you can look around a bit.
also it would be kinda nice, to do the creeps/units a hero can summon a little different to the ordinary "you control em" way:
there might be 2 (or more) types of creeps: commanders and creeps.
Commanders and heroes each can have a few creeps around them, but the number is limited (heros can control more than commanders)
creeps can not be controlled, except by giving orders to them via a hero or commander (spellbook, that contains orders like "protect"(unit), "guard"(position), "move", ...) As long as they areen't given any order they stick to their comamnding unit (hero or commander)
i hope you could unterstand what i ment, for i did not structurize my idea that much - more kinda typed it as it came to my mind ^^
- raszul