Honestly, if you’ve got a sense for when it applies (of the words in the blurb, only Keith and counterfeit are actually exceptions), it can be pretty helpful. I learned this:

I before e except after c

Or when sounding like a as in neighbor and weigh

And weird’s weird!

And it applies only to words with an e sound that isn’t a diphthong, and not to words that are recent arrivals from other languages. If you’re using it to try to spell “hacienda,” it’s worthless. If you’re using it to figure out “conceited,” it’ll help.