They will eat you up if you aren't responsible enough with them. Thats pretty much why they exist I believe. My family has paid nearly every expense for the last 3 years on some kind of rewards card, but I'm in charge of expenses and I monitor the balance daily and pay it off during the week online to stay in control of the budget. Almost like a check register that I'm not having to physically write down.

With the rewards junk, we had a Disney card that we ended up with $1050 that we used on all expenses on a Disney trip last spring. I paid $4 out of my own pocket the entire week towards basically any of the overpriced junk you could get there for a family of 5. Food, drinks, souveneirs, whatever. Made that ridiculous vacation affordable as everything at Disney is ludicrous expensive.

After that I got a Cabelas card and 2 weeks ago put $550 towards a Browning Hi Power that also gained back an additional $260 in Cabelas points on that purchase during a special deal (5X club points at 5%= 25% points gained).

Its just whether or not that kind of thing is for someone or not. I'm a meticulous freak on the budget so it works out for me.