I've been using square since their first mag stripe reader. It's always worked well, especially when friends owe you money and say they don't have any cash on them, haha.
Here's a video of setup and a demo transaction with the new reader:
I had a garage sale a few months ago when I sold my house. Having Square available enabled me to sell a bunch of big ticket items that people were interested in, but didn't have enough cash to buy.