You definately did not shove 25 bucks down the drain. Unlike a lot of shareware, its not terribly limited in the free form.
One important thing that it does is remove the
http://www.game-maker.com watermark from your games.
If you are looking to create professional games, and lots of people here have, its important that it look professional. Nobody, or few people, are going to buy a game that shows that! After you register, there will be no sign at all that you used anything but pure C/C++ to make it.
The software is pretty good stuff. I already knew C, so I didnt need GE. Its the community that kicks ass. Plus having it all layed out and easy to prototype stuff is great.
Maybe those are not good arguments. I'm betting that a whole bunch of people, like gogo, sparky, tekdino, d-soldier, and lots of others will speak up and say its not a waste of money at all.
Welcome to the community.