Rated 3 out of 5 stars
I have installed the beta version 1.15.1b, the result is better but I still have a permanent CPU load between 10 and 20% of one core, which disappears if I deactivate your extension again (with FF Mac OS X) with the same tabs active (one forum, gmail and igoogle).This review is for a previous version of the add-on (1.14.0). This user has 2 previous reviews of this add-on.
Sorry to hear it's still eating your CPU. The extension does do some polling of the Gmail page to listen for interface changes (listening for compose, inbox, etc). This happens every half second or so, so I am not surprised that you are experiencing some increased CPU usage. That said, it may still be using more than we would like. Perhaps I can add an option to change the polling interval so that it doesn't check so frequently for people with slower machines.
For what it's worth, BC Gmail Sigs v1.15.1 in Firefox 4.0b8pre my CPU usage on the Gmail inbox page is about 2-6% on my work computer. It uses 1-3% of hte CPU when running in the dev build of Google Chrome. This is definitely worth revisiting. Thanks for mentioning it.