I've not used the A710, so my comments may not be applicable to
that camera. However, if the IS in it is similar to the Canon S3IS
which I have used before, it should be quite effective.
Basically, IS in the S3IS would be able to gain you a two stop
advantage in shutter speeds. This means that if your best
handholding technique occurs at 1/30s shutter speed, with no
handshake noticeable at a fixed focal length (or in layman's terms
"your zoom level"), IS will be able to take you one stop lower to
1/15s, and another stop to 1/8s. So your handholding technique
"improves" with the help of IS.
To learn more about IS, you may visit here: http://www.kenrockwell.com/tech/image-stabilization.htm
The effectiveness of IS is measured by the number of stops it can
help you, and if I'm right, IS in the A710 should give you a two
stop advantage. In DSLRs, IS may even grant you three to four
stops. The Nikon term for IS is VR, Sony/Minolta's AS, Panasonic's
OIS etc.