Late ultrasounds harmful!??

I've heard and read that ultrasounds can be very harmful for your baby. For example, a study by dr. Sarah Buckley MD done in 2009 states, that there are many "potential biological risks to the fetus from prenatal ultrasound." 
Personally, I've always been very excited to get ultrasounds, as this is my first baby, and I want to see and hear the heart beat, see if the baby is measuring correctly ect. But is this really what is best for the baby?
Ladies: what do you think, are ultrasounds ok? Or should we try to stay away from them if possible??