Has anyone experienced using both the Canon 100 macro IS and non IS.
yep
If so, would you say the IS version is worth the extra money?'
yep
One thing to consider is weather you would shot mostly at Macro distances or mostly further away - the reason being that at macro distances around 1:1 the I.S. is not very effective (about 1/2 a stop at best), it is only when you are shooting further way that you will find the I.S. becomes very useful.
I am not sure I'd use the IS for macro, but a 100 macro is a very useful non macro lens as they tend to be blisteringly sharp and that is where the IS will help.
The IS is not the only difference between the two. The L is a more sophisticated beast with higher performance.
yet the IS unlike many L lenses is made of plastic