One thing from the N900 that I really miss on the Pro1 is the ability to multi-boot different operating systems. I think at one point I had five OS's running on my N900, mostly off of various microSD cards - Maemo, Android, Meego, SHR and Plasma Mobile. For the Pro1 I'd settle for being able to dual-boot Sailfish and LineageOS, but as it is now you need to pick one or the other.
Many people in the community are getting around this limitation by running virtual machines of the various operating systems they want. With the modern processor (compared to the N900) and the 6GB of RAM, performance seems to be totally usable on the Pro1.
