Last year, I switched my main credit card to MBNA's SmartCash credit card (see my post). At the time, I estimated that I would get back about $360 in cash for the first year (taking into account the sign-up bonus) and $288 for each year after that.
So I did a quick check-up on how much money I got back since signing up for the new card. By my calculation, I actually got closer to $400 back. Based on that, I can probably expect something like $300 every year, which is 50% more than what I was getting back with my old card.
Not bad at all.