The theory is not only useful, but essential to categorize life. A biology student could not make sense out of all the different species of plants and animals without this "tree".
Biologists take significant genetic and fossil evidence and look backwards--but when they try to take that same evidence and move forewards they start making claims that simply cannot be drawn necessarily or absolutely from that same evidence. They can make a plausible explanation--but that it all.
If I may make up a term (biologists do it, too)--I'd like to point at a notion about speciciation I'll call "fortuitous coherence"--rather like the coherent layers of light piled up to create lazer light. Fortuitous coherence is necessary to accomodate your theory of speciation--on top of fortuious accidents happening in fortuitous order. This is why duplicating speciation is so difficult in the laboratory. And when I worked in a lab many years ago, I was taught that "reproducibility" was a very high value when testing scientific theory.
In short, get that monkey chart outta my face!!
As far as the spiritual dimension, it bothers me not at all that things in the Bible stretch the credulity of scientists. They seem to think that a "fish" swallowing a man presents some unconquerable challenge to faith. They ought try dealing with the heroic little children in an oncology ward. Talk about something to test your faith--the Garden of Eden is child's play after that.
I've said it before: If people where descended from cats, which are clean and pretty, we wouldn't oppose evolution so bitterly, but because we're descended from ugly, smelly apes that scratch themselves and masturbate in public, we resent the connection. I think many people's objection to evolution is neither religious or scientific. It's aesthetic.