What happens when .....

..... the IS fails on a lens ? Is the lens rendered useless ?

It's still good on a tripod, right? Or handheld at faster exposures?

hammer418 wrote in post #8474686
..... the IS fails on a lens ? Is the lens rendered useless ?

No of course not. It's just upto you if you want it to stay that way or get it repaired by Canon.

My housemate has a 17-55IS and the IS mechanism broke, as in it doesn't work anymore. Now when he tries to use that lens on his 20D, every image he tries to take gives him an error.

Guess it depends on exactly how the lens "fails." There just are not many cases of IS failing so if you are thinking about getting one - relax and buy it.

Thanks for the early feedback, folks.
A friend is considering buying an IS lens, and I'm trying to find actual user experiences (good & bad).
I'm also curious about my original question, as I wonder if IS failure leads to 'lens failure'.
I realize there are probably various degrees of 'failure', but am unclear whether the lens is able to focus at all (NO- in fayenatic's friend's case),
either in Auto-focus, or manual-focus)

It becomes a non-IS version

You have to decide whether it's worth the cost of repair.

I'd say it depends on how it fails as well. Sometimes it may be usable, other times it may not. Thankfully I haven't had any problems from mine.