Yes, that's correct. I've tried the official Sprint Wi-Fi tethering on an HTC Evo 4G for a couple of days and I was only charged for those days. The device supports up to eight wireless connections. Setup was over the phone and was effective immediately. The last time I did this was in early 2010 and the experience was flawless. It's overall not worth the money to me, though, to leave it enabled permanently. There are some USB tethering apps that require a little client-side setup but they've worked for me as a casual single client solution.