Well I am a guy that had a nokia n900 for 1 and a half year and after the usb breaking down, I moved to galaxy S3...

Personally I think that n900 is only good(right now) more for using it as a tablet!
It is not that fast as many, many other phones out there and it can be a little annoying using it as a primary phone. I don't have a jolla, so I don't know how it feels like in real hands but I think that it is a good alternative for moving on if you don't like the android/iOS phones.

For the Sailfish OS (from a small port on galaxy s3 that I had installed) I can say that it is a great operating system and it should be keep updating! It should be a pity to see it going down just like what happened with harmattan(another beautiful OS!)

The only "bad" thing about jolla is that there are some complaints about the support, and the hardware that is used is a little more outdated considering the phones right now, but yet it is not bad! Plus you will have the other halfs, something that is unavailable to other phones!

As bluefoot stated, I would prefer to have an android phone with a port of a fully working sailfish OS(with the ability to install android apps on it as well), this could be the best choice I think...

P.S.: I hope to get a n900 in the near future as well! I really like that phone and I think that it is a legendary phone! After all, I like all the twerking that I was doing to it! Maybe a n9 would be cool too for me(it was always my "dream phone", I don't know why )