I use it for downloading torrents without leaking my IP. If you can’t portforward you are limited to downloading torrents. You won’t be able to upload, or at the very least your upload speeds will be very slow. If your primary use case is torrents portforwarding is important. It allows you to open a port and be able to upload.

Mullvad is a great vpn, one of the best for sure. Unfortunately because they don’t support portforwarding the product is not a option for me anymore. I switched to airvpn and am satisfied with it.