My experience is with the Nikon equivalent (105mm VR). The IS/VR performance of the Canon and Nikon lenses are reported to be very similar, so hopefully this will help.
Everything I read about the lens before buying said that VR was ineffective at macro distances and autofocus wasn't much use either, as it would hunt and you should be using a tripod anyway.
Well my experience has been quite different.
At closest focusing distance (1:1), image stabilisation has some effect, but very little. AF does work, even at 1:1, if you have a good contrasting edge and use a single focus point. I don't tend to use AF thought as it will sometimes hunt, and that's frustrating.
However, most of my macro images are not taken at closest focus distance, and for these close, but not quite 1:1 subjects, I find image stabilisation is very helpful.
For bugs: many move too quickly or will run/fly away if you get too close, so you may have a hard time getting to 1:1. I've taken handheld shots of houseflies at 1:2 using VR. It may have only given me a stop or two, but I believe it made the difference.
Flowers: except for the occasional abstract shot, 1:1 is too close, for most of the images I take anyway.
Indoors: hopefully you're not chasing bugs indoors. Most things I shoot indoors are inanimate, so especially with the light it's best to use a tripod, so IS not that helpful
Tripod: IS not necessary, and in some lenses can cause motion blur rather than reduce it.
Outdoors: except on a sunny day with aperture wide open, where IS might not be needed, if you stop down, or it's cloudy, your shutter speed will be in a range where IS can definitely help.