I'd not use it. The "free" aspect of it worries the hell out of me, they have to make money somehow. Then there is the fact that it is "peer-to-peer" that means that at some point your machine/device will be used as an exit node, and as soon as that happens all bets are off. You'll probably have the FBI knocking on your door pretty soon asking why your IP was used in some crime or another, assuming they ask before arresting you...
Free ALWAYS poses some risk to you, but in most cases it's just advertising, but in others it is far less clear.
If you are looking for a VPN then look for a solid reputable one that is not free (in most cases they are less than $100/yr). You'll be much better off.