I haven't tried it but I've thought about it.
I mostly have a Scene VISA with a ridiculous amount of free movie points, I use it for all my work travel and stuff so I haven't paid for a movie or snacks in like... 5 years? and I go pretty regularly but there might be another card that offers better rewards.
I also have a Costco card and they send me a few cheques every year for a couple hundred or more.
I've never bought gas there, it definitely is up to 10 cents cheaper a litre but, in my town at least, you'll end up sitting in line for 30 minutes so the savings isn't worth it for me, my time is worth more :P