Fantastic! Rated 5 out of 5 stars
I love this extension! It allowed me to get rid of the shonky usercontent.css hacks that I was previously using to achieve a similar effect (but much more limited).
I was worried that the icon display would somehow be laggy and sluggish (which would have really annoyed me) but it's not at all.
The thing I like most is how comprehensive the options are. You can change any of icons to ones of your choosing and position exactly where the icon should display using the pixel offset setting.
The only slight downside, as others have already said, is that you can't use negative X & Y offset values to raise icon position or move it to the left of the pointer icon. Other than that, it's all good. 5 stars.