Incredibly useful extension. Surprisingly responsive dev team, implemented requested features/fixes within 2 days of email. Would only be better if it was open source.

I especially like the steam wishlist feature, which allows you to scroll through hundreds of your wishlisted games and see the best prices without even having to visit the page.

Perhaps a little overzealous, even integrating with youtube and twitch (seems overkill), but you can configure what sites it works on.