Let's not start that debate again. I have an AEM with the A'pexi dry filter and no CEL. Back to the original question, it's not worth it for just one CEL, but if you get them all the time, then by all means yes, it is worth it. Nothing like knowing the code before you take your car in for any CEL.
i alwaysjust take my car to autozone, they check it and clear my code for free, i wouldn't buy one unless it was real cheap, like $50, and I have seem them on sale at autoparts stores for like 89.99 so i would look in that price range, good luck, TIM