It's a good service and I've used it a few times, but the requirement to use an extension is a bit of a pain point.

Especially as the extension seems to try and install some adblock style stuff which I already use ublock for and overwrites the default search engine with no option to disable it. Every time I need to generate a new email I need to re-enable the extension, copy the email address and then disable the extension again. Not nice UX.