No, it will not function exactly the same, because it sends stuff through your server. That is a very important difference.

Leaving my front door open when I'm on holiday also makes more things possible. That does not mean I will like those things.

Don't take me wrong… I would use your service in any proof-of-concept/mockup/prototype… It really helps a lot in those use cases, since is one less thing for me to worry about.

I just don't trust it enough to use in production.

I don't doubt that your service works with the best intentions, but why should I open a security hole in my application, when I can easily avoid it by writing my own proxy and keep it private?

What happens to my application, if your service goes through a DDoS? What happens to my application, if you suddenly decide to close your service?

I'm pretty sure you can use these arguments about other services, but this service exactly, is not worth the risk.