I guess it boils down to whether we think it's "lip service" to start work on a new concurrent project before the initial project is complete. As a freelancer, I work on many projects at once -- am I being unethical by dividing my day to several tasks in parallel instead of performing them completely serially on a first-come, first-served basis? I don't see that there's any neglect inherent in using some resources to explore avenues not directly related to the game. Is it also unethical if notch buys a luxurious replacement for something that he had previously owned which was adequate but not luxurious? Is this also a waste of the "advance" given by players?

While notch intimates that there will one day be a "final" version of minecraft, the only way that effects any minecraft owners is that they received a discount from the theoretical "final" phase because they purchased during testing. There is no contract or implication that final is going to be released no matter what, no refund available to users who don't receive a 1.0 as soon as they'd like.

I think it's silly to consider that an ethical violation. People who buy minecraft buy to play as it is, NOT to play at some hypothetical future state. It is not an advance where we receive a half-finish product with the promise of a finished product by x date.