Simple welds are pretty easy for many to do, but I totally agree that it takes someone really good to get a pretty weld.
Something that happens with inexperienced welders is that bubbles within the weld itself can weaken the weld, and a stress fracture can happen in it later on. Also, if you don't get the weld bonded between the materials being welded together, it can be weak also, so your welder friend isn't totally correct.
Welders that work on pipelines are artists. Their welds are barely noticeable to the eye, yet they're strong, and many are even inspected by x-ray technology, to ensure that they won't break or leak. A good weld should not only look good and be strong, it will also be gas and air tight.