I don't know about other fans, but I personally think that Starbuck should of ended up with Athena.
For one thing, she's prettier!
Also I got the impression that he actually loved Athena, but pushed her away because he knew she was the perfect girl and was afriad of being tied down. With Cassie he knew there was no real chance for commitment so he leaned more towards her. I'm not saying he didn't care for Cassie, but he didn't TRUELY love her that way IMHO.