What made you think of doing something like ES? The lack of features Steam has in place?
Well it all began during the Winter Sale of 2012. By that time I had already been through a few of the "big" sales (Summer 2011, Winter 2011, Summer 2012) and had I think about 700 games in my Steam account.
I got increasingly frustrated with browsing Steam, seeing great deals, and having to click each page to see if I already owned that particular game. First world problems, I know! So I set out to find if someone had made a script to just... show me which games I already owned when browsing the store. I mean, Steam had been around for a long time before I opened my account, surely someone had made such a thing. To my surprise, there wasn't anything like that I could find after hours of searching. I spent more time looking for a script like that than the time / clicks I was looking to save.
So I decided to make it myself. It started out pretty ghetto, but I shared it with a few of my friends (who also had larger Steam collections) and they really loved it and started using it and requesting new features. It's pretty much been that way ever since - I'm constantly coming up with new ideas of things it can do, or being asked about new features.
Looking back at my old code, I can definitely tell that I've improved greatly in my skills since then, and I've learned a lot about extension packaging for different platforms.
It's really been great and I've always had great fun with it - I could honestly see myself working at Valve for the rest of my career if given the chance. I don't think I'll ever get tired of improving Steam.