I would go for it.

I have been using it since Dec 2013 and it makes for a great smartphone. There were some basic features missing initially, but since June or so, everything I need is in place (yet updates keep coming). Mind that it is not a replacement for the N900 - it doesn't have an FM transmitter, IR port, stylus or EasyDebian and typing on a touchscreen (in general) is a PIA. On the other hand, there's a qwerty keyboard coming up which should really help the usability.

If I were you, I would buy both Jolla and the TOHKBD (keyboard). It is the only choice if you want an open, hackable Linux device and real multitasking.

PS: I am also a former N900 user and I bought Jolla just to support the company and I never expected it would replace the N900. I was therefore astonished by its completeness and ease of use. I still miss some features of N900 (mentioned above), but those should eventually come as well.