I charge everything and pay it off every month. Haven't been bit yet. Why not? Because it's up to me. Doesn't cost me anything since the transaction costs are rolled into the prices from the vendor, the points are a nice little treat for spending money I would have spent anyhow. I'm not going to get rich off them, but I'm also coming out ahead when compared to a card that doesn't have points.
BTW, if you're wondering why some vendors don't take AMEX, it's because it's a lot more expensive for them than other cards. Haven't seen any sign from our end of the different rates for different flavors of Visa, though. I do know that we get a better rate if we collect all the info such as the CID instead of just the card number and date.
And yes, Tuna, that shiny coppery square on one half of your new card is the chip. Next time you go to Walmart (and an increasing number of other vendors), expect to be asked to insert that into a reader instead of swiping the card.