In my experience, EKGs are terribly dependent on the tech who applies the electrodes. Also, EKGs can give a lot of false positives.
But they are valuable. They are a screening technique, and in general, their value is that they are a way to look for anything funny that might be going on in the heart department.
If you don't have weird symptoms like fainting for no reason, or breaking into a cold sweat or barfing while walking up plain old stairs, you're probably fine. But I think it's a good idea to have a good cardiac workup when you're in your 30s, just for a baseline. Who knows? Sometimes, weird stuff shows up that can be useful as time goes by.