They've *seen* evolution. I can't remember the scientist, but he's had some bacteria growing for like 30 years. They eventually, after thousands of generations, developed a new trait (the ability to eat something that their kind had never been able to eat before). The fact that their kind *couldn't* eat whatever sugar or whatnot that they evolved to eat was one of the defining characteristics of the species...until they evolved around that limitation. The scientist had saved all the generations (in frozen form), so he was able to go back to the generations before they evolved the new trait and restart that line, to see if they'd evolve the same trait again. I'm not sure if they ever did, can't quite remember the rest of it. I don't think they did though.
Also interesting (it's starting to come back to me now) was that the new species *almost* died out. Not quite, but boy, it was close. The population of the bacteria that could now eat the sugar shrank almost to nothing...then exploded and overwhelmed the un-evolved bacteria, which didn't have such a ready source of food, and were quickly (in terms of generations) rendered extinct (within the confines of that jar anyway).
The amount of evidence that supports evolutionary theory is overwhelming, and spans all sciences -- physics, biology, anthropology, everything supports it. Oh, there may be a flaw here or there (like, it's not so much of an evolutionary TREE but rather more of an evolutionary bush), but the *overall* theory isn't questioned by many at all anymore, at least not by those with an education.
The foundation upon which evolutionary theory rests is as strong as that upon which the Theory of Relativity rests. There are flaws with both, but only in the details, not in the overarching theories themselves.
Creationism is not a theory. A theory is testable, and has repeatable results. Because there is no way to test the "theory" of creationism, it *isn't* a theory. Which means it isn't scientific. It's based solely on the faith that, yikes, stuff is complicated, therefore some omnipotent being musta done it. People of two hundred years ago would have looked at a Maserati and thought the same exact thing.