Outside of restaurants, no one looks at cards anymore in my experience. Might be different if you buy something big I guess.
The attachment to the phone is nice for security, but the idea that if some reason my phone's battery went dead, and I needed gas or something and couldn't buy it until I got my phone charged puts me off. Nice idea, but not quite there for me yet.
Just keep your regular cards in your wallet as backup!
Fixed to hopefully make my post clearer for Lee.