Excellent post! Most advice I see on theme development is absolutely horrendous.

My advice to newcomers is to focus on the basics. Most new folk don't learn the fundamentals of HTML and CSS and run into really weird problems because of it.

The only thing I disagreed with while reading your post was "Theme development was also far simpler during that time. With a handful of files and templates, you could build something special". IMHO, you can still create something special with a few files and templates :)