I am a bit surprised by the design choices they made: When I receive just a few sat, the Phoenix guys open a channel for me, and pay the on-chain transaction fees! On-chain transaction fees are currently very low, but it's still 246 sat, which is considerably more than the few sat I deposited. If I would close the channel, the Phoenix guys will lose money on it again. Their fees are really low so I hope this will be a profitable business model in the long run.
If everything works as they say it does, I'm quite impressed! It is indeed much easier than opening my own channels in Eclair.
However, it leads to many questions: right after my first incoming LN transaction, Phoenix opened the channel. But the channel isn't instantly confirmed, but it already allows me to make LN transactions. I have no idea how they pull that off.
Phoenix says the 12 seed words are enough to restore the wallet, that means they somehow link my open LN channel to those seed words (because the wallet is not custodial). Here too, I have no idea how they pull that off. For small amounts I'm totally fine trusting them, but for larger amounts it would be a good test to see if I can restore my channel in another application (again: I have no idea how).