I wouldn’t describe it as important, but it’s certainly beneficial. There are only so many combinations that are available using the keyboard, and while I would usually navigate using the keyboard, I find that I perform certain actions with a mouse all of the time, like clicking on links in the code.
I recall Ctrl+Click being a common command to follow links in a few older apps (like Frontpage – eugh) and I think it works well, so yeah, the ability to hold a button and click would be beneficial, but it would only ever be used for a couple of functions I’m sure. I don’t call it important, but I would REALLY love it :D
Cheers