I'm really disappointed that the article didn't mention what is probably the single most important characteristic in an opamp when being chosen by an amateur:

Unity gain stable

Sure, the other characteristics are important, but a whole bunch of circuits that beginners are likely to use rely on opamps being unity gain stable. If they're not unity gain stable, the circuit will do very weird things, and a beginner won't know why.

Of course, debugging issues like that are how you eventually become an expert.