Using abilities of N9. Listing in descending
1. You know, if you wanna have a lot of fun with POWER OF LINUX (learning of basicsc terminal,developing your IQ and ability of fixings) enjoy wirh pleasure!!! In this case the best gadget!!!

2. You can also use it as main phone (in most case), as it said it comes from the box with everything what needs to be as a main phone. But, one but, the but is that you always have to understand and keep in mind that this is yes 2011s phone flagman but using in 2014.
a)Calls - everything you need to call+free call recorder+not bad speaker,hearing good.
b)contacts - unlimited memory+sync your Nokia/Google/Facebook/Twitter...and much much more(very good for 2011s smatphone in 2014)+you can view all of contacts and can show each accaunts contacts separatly - very usefull,i loveit
c)messaging - too! + you can messaging in your Messages app not only via SMS but with all of your contacts synced from your accaunts-no need to go to Facebook (example) or some else social site,just sit and recive/sent your messages to your social acc contacts.
d) camera+gallery+player - good quality+taggs,geo,beatiful gallery viewing images+not so functional,but enoughly if you wanna just listen music(dolby quality)
e)and very beatiful UI with just swipping - this is the pleasure for me to use N9, just swipe it and it gives me pleasure just swipe and close,just one swipe and swerve the window. As it said - Love at first Swipe
but ofcourse not so functional,not so strong battery life as 2013-2014 smarts,but again yes still useful - it can be used as main phone!

3) you can not use and accustom Meego Harmattan if you came from EASY using,not friendly for fixing issues then you absolutely do not buy and then dont crap this beatiful device - this device loves those who love to fix issues

about other OS's - Nitdroid port is older than Sailfish port,so for now its (Andorid) working better than Sailfish on N9 and better than our also lovely N900. About what is not working, please make a search and read (read read and read) about what is working,what is not working for now and what will never work - go to nitdroid site,find the latest relase (for now it Alpha 5) and read all about this. Im using quadruple OS on my N9 -meego(full working)+android(80/90% of phone functionalities working)+Sailfish(60/70 maybe can be said 80% working)+firefox os(60/70% working).

and all of these was wroughted from my N9 64GB Also plus is 64GB.

PS: if had enough money i would be continue this device and this OS manufacturing and developing (in global power) but i dont have money for it ) if this OS will be developed and supported by Nokia in it full power this device and OS will be the best usefull featured OS for now,more than android more than ios....Oh God, where is justice