That's hardly the case is it. This is the old deist argument for god. According to Darwins theory, there's nothing accidental about natural selection so your point is what?
Who cares what Darwin knew or didn't know. His claim to fame is that he was the first scientist who tested the theory and had the guts to stand by it, in spite of it being very shaky at the time. He unlocked and opened the door, but only a crack. Others after him found the serious proof, ripping the whole door off it's hinges. We've got many times more evidence suporting Darwins theory now than we did when he was alive. It's no accident that the theory wasn't fully accepted by the scientific comunity until well into the 1920'ies. For good reason. Darwin was wrong about a whole boat-load of stuff. Let's focus on what he was right about.
I belong to the crowd who think DNA easily can form spontaneously anywhere. Even in vacuum. This is based on one experiment made in California, so it doesn't really hold water yet. My point is, be careful with saying that things cannot come to be through natural processes. Chances are that they can. There's a big difference between improbable and impossible.
The problem is that intelligent design is just taken straight out of thin air. It's not backed up by anything. If your only case is that you can't imagine it coming to be naturally, it says more about you than the theory of evolution. Argument from ignorance is not valid in logic.
And then you've got the next problem, in that the "designing" isn't particularly intelligent. It's as if our creator couldn't make his mind up if humans should be quadrapeds or bipepeds, so we ended up being something in between, resulting in most humans having back-ache from ordinary life. Why is our vision centre at the back of the head, slowing down our response time? Our most critical sense being in our most vulnerable place in the brain. There's stupidity everywhere in our "design". And it gets worse if we move to other species. The closer you get to the cellular level it gives the impression of being more and more random.
This pretty much catches the whole point. Yes, we need to be open to all possiblities, which is important within science. But I think we can wait with taking intelligent design seriously until it at least has a coherrant logical model.
And then you've got the problem that Intelligent design isn't really a theory at all. It's more of an anti-theory. Saying that something else, (ie god or gods) has it covered, isn't saying anything at all. All it tries to do is point to the holes in Darwinism without having anything else in it's place. The intelligent design people make no claims at all as to what god is or how it did it. Considering the overwhelming evidence that suports evolution Intelligent design as a long way to go before being a credible competitor.
Regarding speciasation. Science hasn't decided what defines a unique species yet. It's got more to do with politics than biology. In my ears, the debates between scientists so far tend to be extremly silly. They're all on the who-gets-to-get-their-name-on-what level. So it's not clear what you mean by the term. It tends to shift between kingdoms. Let's agree here in the thread that it means stable reproduction of a distinct creature. It seems to me, what what you mean by it?
I have a vivid memory of a discussion, (over a few beers) with a fish expert I had this autumn about a stream in Sweden. In the 18'th century they had one species of fish living in it and in the 20'th century had 4 different stable species, all in different sections of the stream. But beer was involved so I won't swear on having the details right. So I'm not so sure about your claim about specisation never being witnessed in nature. I'll e-mail him for the name of the fish, (if anybody cares).