Never spend more than $250 on the N950, it's not worth it.

If you want to use it as a "better N900", there are many problems with the OS vs the builtin keyboard making it a pain to use. Reception is also _quite_ bad when compared to N9. Besides, first-batch N950s LCD tend to die early, and you won't be able to find replacements. No public schematics either.

If you want to use it as a test device for N9 development, then it's also useless. It is way too different from the N9 (screen & color reproduction, aegis, accelerometer, USB hardware...), so you will eventually need the N9.

I can only think of two use cases for it:
A) Museum exhibit / Collector's item / Collecting dust in a shelf
B) Testground for non-Harmattan OSes such as Mer, where you might not care if half of the LCD is broken or if it misses phone calls.