I’m also interested in hearing Proton users’ experience. On paper it looks like an okay deal, but you could get a similar suite of services from Posteo + iDrive + Mullvad + BitWarden for cheaper and not end up locked into an “ecosystem”.
However, there is legitimate value in combining email and drive space. Posteo only gives you 2GB for email, and their upgrades are rather expensive.
Also, Mullvad might not be equivalent since they axed the port forwarding feature a while back, making BitTorrent only kind-of usable (incoming connections will not work).