I have 2. One in the wifes maiden name, and one in my business name. Very convenient and it will email my customers a receipt (and myself) immediately. The money is in my account that night!
Interestingly, they say that as long as the total yearly amount is under $20,000 and under 200 swipes (I think) then they don't report it.
The reader is free but there can be a very long wait for it. They sell them in radio shack and target and walmart for $10, and square will give you a $10 credit. Target sometimes has it on sale for $5 or $8, so you would actually make money on the deal!