I had a stress echo five months after my heart attack; it came back clean.
On the one hand, it's just a diagnostic to make sure that you're as healthy as you think you are. If you are, great! If not, it's a chance to catch something before it really damages your body. (Do you get stressed when the nurse takes your blood pressure?) And it's probably safer to uncover a problem in a lab with loads of medical personnel and a crash cart standing by, than climbing a remote hill 15 minutes away from an ambulance and in a cellular dead zone.
On the other hand, if the doctor suspects something, (s)he should be able to point to something; high cholesterol, poor circulation at your extremities, even a wiggle on the EKG. I wonder why you're looking at a stess echo rather than a cardiac cath. But I'm not that kind of doctor.
Chill out, get ready to run (or at least walk fast), and ask if you can watch the screen. I was sure there was something wrong because my heart was moving around so much, like watching a gymnast on a beam. But the techs and the doctor were completely unimpressed: yeah, that's a normal echocardiogram.