In short, I used to find my hands pretty steady, since I can hand held a pair of 10x50 or even 10x70 without major issue. I can hold them quite long, and I found the view quite steady, at least the vibration will not be annoying, I can resolve pretty much detail from the targets which I observe.
However, when I press the button my the Canon 10x30 IS, wow... I know my hand is quite shaky, the vibration is not very bad, but it definitely washes out some small detail. When the IS button is engaged, I can resolve some more detail from the view, and the small vibrations are all gone!
At the first few usages, I found after pressing the IS button, the view becomes a bit strange in a sense that you can feel like floating on the sea, I even got a bit sea-sick after several minutes of usage. However, such feeling goes away soon after just one day. I get used to that feeling.
Like most people comment on the IS button, yes, we will need to hold the button down to enable the IS function, however, it's so easy to hold it, you don't feel tired even if you use it continuously. So, it's not an issue indeed.