One thing I noticed was that I really need to learn how to use the STL properly. I'll probably order Effective STL off amazon in the next day or two, but it'll probably be about two weeks before it arrives.
In restructuring the article's code for clarity and accuracy I've seen how my current engine's design could be greatly improved. I'm not going to do it now but after the game I'm about to start work on I'll sit down and refactor my engine.
I got started on testing out the sound system today, so I'll finished that up tomorrow.