I actually found it to be good practice for when I bought my first car.One.
I think that if you treat such a card as a proxy for cash you already have (similar to a debit card but paid once, in full, on a monthly basis), and you keep careful track of your spending versus your savings, then there is no problem; you know very well the money is on hand and you can handle it. But using it to spend yourself into unsustainable debt...I want no part of that.
That's why I like my store cards more than a traditional credit cards. I use them to make major purchases, like my TV, which I know I can pay off over time. I don't necessarily have $1000 to drop on a new TV today, but if I put it on my Best Buy card with 18-months interest free, I know that I can definitely handle making those monthly payments.
Oddly enough, thus far I have made all of my biggest purchases in cash. That's what I'm planning to do again this year, whenever I buy a new laptop. That'll change whenever I buy a house or a new car, but I've tended to use the credit card more for smaller stuff.