Great, I think this was my first keysend transfer actually! It feels unfamiliar doing Lightning transfers without invoices interaction, but also super practical and cool!
It does come with some
drawbacks, even though I understand none of them. "Inability for the payee to specify their preferred
min_final_cltv_expiry"; why is true for keysend and not for invoice? "Loss of being able to use the preimage and invoice signature as proof-of-payment"; again, which part is different and I don't get the pre-image? Isn't it a core part of Lightning to get the pre-image? Isn't there a payment hash involved?
One drawback I expected to see but didn't is privacy. To send with keysend, you need to reveal your node's public key. With invoices, that's not necessary.