Depends on the coffee.

I developed a sensitivity to caffeine, it basically throws me into a weird heart racing thing at any but the smallest doses.

But I freaking love coffee. So I buy decaf. If you shop around, find a few brands that do water process decaf, you'll end up with something that's good. Not just good enough, but good.

But the chemical process decaf, yeah, I can tell a difference blindfolded. Literally, I won a bet doing it.

The typical name brands, they usually have a fairly over processed taste to begin with. So it's harder to detect, and I can't tell the difference as clearly. It's there, but you have to already have compared them before you can tell blind.

Thing is, part of that is how you drink coffee. If you're drinking it out of habit, or on the go, your brain is going to filter the taste out in favor of other sensory input. You have to be drinking it for the coffee itself, paying attention to the experience.

Chemical process decaf has this layer of unpleasant metallic tang to me. Water process tastes like the same basic roast and bean, just slightly less intense. Things like floral notes get a little muted.