Speaking as someone much much closer to a fan boy than a hate boy (I make my living on Apple's platform), this is...possible, but with a lot of caveats. It's nowhere near the level of control you have on a desktop machine.
- The signing expires every 7 days, meaning re-install once a week. The app just crashes on launch when it expires.
- There's a (low) limit on the total number of apps you can have installed at one time via this method. I believe it's 5.
- The Apple ID you're using to codesign the app has to be signed in on the device to which you're installing. (I may misunderstand this one -- been a while since I've done it and it may have changed somehow -- but I'm pretty sure about it.) The implication here is that to share the app to anyone else, you also have to share your Apple ID.
- You're still beholden to Apple. They can revoke your Apple ID and thus your signing privilege pretty much any time for any reason.
They've restricted this avenue enough that I think it's fair to say it's not functional as more than a teaser, for people just checking out iOS development.