What is good fermentation temperature control?

Hi Guys,
I am really trying to fine tune my brewing and with that my fermentation temperature control. What do you consider to much of a variable in temperature? I am currently putting my carboy in a large plastic tub filled with water. I am using an aquarium heater to regulate the temps but even using this method I notice a 1-2 degree swing sometimes. Now I now this is OK for good beer but I am trying to make "great" beer. How much temperature "swing" do you get using a fridge with temp controller? I would think you would still get a small swing. Thanks. Al

I have my temp. controller to come on with a 1 degree difference. So, my fermentations should be within 1 degree of what I want...give or take.

I'm no veteran brewer, but chemically +- 3 degrees or so shouldn't hurt you a bit, as long as it doesn't go high enough to kill anything you don't want killed.