They're great to teach about mining. I use mine as a forever lottery ticket. Every approximately 10 min, I have a 0.00001% chance of finding a block.

If you join a poll, I believe you can make about 60-ish sat per day. It may not seem like much, but who knows their value in the future.

Personally, I don't regret getting a Bitaxe. It's fun to have and play around with.