Some retailers offer great deals on store financing on everything from appliances to carpet. However, you should read the contract carefully. If it offers "90 days same as cash," for example, and you don't actually pay it off before the 90 days end, you may owe a high rate of interest from the date of purchase and going forward.
You may be better off using a card with an introductory low- or no-interest rate. At least then you only pay interest after the introductory period ends.
Always pay more attention to the interest rate you pay than to rewards rates. Rewards are great, but paying high interest rates will cost you far more than you save.