Sorry if I wasn't clear: you CAN use the service just (about) like it says in the MR article. You don't HAVE TO sign up for their service. But in that case, there's still the issue of replies -- they just see your email address. I'm a little paranoid, and after testing it with my real email address that contains my full name sent to my iPhone (it worked) I was worried that I had just given some unknown site my name, email address and cell phone number. So I went to their website, and looked at the instructions for signing up for their service, and to SIGN UP for all their services, they require your email password. Since I'm paranoid anyway, just made me more paranoid. (and then the post about their security policy decided it for me -- but that's me. Some people use online keychain services with ALL their passwords including banking) Like I said, it seems for people without email on their phone (but unlimited texting) to get emails as texts.
Yes, it's just as easy iPhone to iPhone to send email, I don't know how the notification will change, though -- text notification is easier to hear and see at the moment, and you can see who sent it without going into the app. People here have posted how to do texts back and forth via email and texting without going through any outside service -- I've never done it.