I'm no scientist. I did actually start out as a biology major back in my college days, but organic chemistry in my freshman year took care of that ambition. Anyway, point being that I'm not conversant on the technical aspects, but evolution has always made perfect sense to me.
I do understand how it is that the theist can look at the wonders of life on this planet and conclude that there is no way all of it could have happened through a natural process; just looking at the intricacies of something like the relationships between flowers and the insects which pollinate them, or various marvels of camouflage can be so mind boggling that they positively scream "creation".
But the thing I always go back to is the genetic links and the clear similarities between the structures of virtually every life form (animal, at least, though we share genetic similarities with everything, if I am not mistaken) out there. Why is this? Why, with infinite imagination and ability, would god use basically the same template over and over and over? Why would everything he created show evidence of specific links? Why would he make it so easy to lay out a map of evolution from single cells to all the diverse life which exists by following lines with, at this point, no real gaps of the sort that one's mind couldn't automatically perceive and fill in the progression?
Now, this argument doesn't refute evolution guided by god. Maybe he thought it was a good game to play, seeing how complicated and diverse he could get life to be based on an original bit of life. I don't suppose there is any way to prove that one way or the other, and it doesn't really matter all that much to me as a sort of borderline deist/atheist, but that's not what this conversation is about.
If macroevolution was not science, to my mind, it would not fit so tightly together and support pretty much all the hypotheses which have been thrown at it, getting more and more complex and specific all the time. I can't even imagine what might be necessary to totally falsify it at this point. It's completely obvious to all but the most closed mind that, with or without a deity guiding it, evolution is the way that life on earth reached the point at which it stands.