Is it unethical to stay at a company, use their tuition reimbursement/prepay to get a degree, then bounce once you've completed the degree?

Is this kind of behavior looked down upon? Do other people do it?

I agree with everyone else in this thread, but the one thing I'll say is that how you handle the exit is really important. People can usually put two-and-two together so when you give notice make sure you emphasize how much you've enjoyed the experience.

Let's ask it another way, would it be unethical for a company to hire you, promise you that they'll pay for your tuition, give the leadership team hefty bonuses during a period of declining growth and profits, and then lay you off 6 months into your contract? Yup.

Do companies do it all the time? Yup.

You're the CEO of your own career. Do what you need to do to maximize your earnings and growth. But, also, don't burn bridges when you move on.

I have a friend who did this, but couldn't deal with the company for the full period and ended up leaving halfway.

The company still paid for 50% of it so depending on the terms of the deal it could be a win-win regardless of you leave early or not.

It's probably fine, but I would be somewhat tactful about you handle it near the end. Maybe don't leave right away?

Absolutely not. Companies hire you and you agree to work there because it's an exchange of services. You're completely in the right to work there for the minimum and then leave.