Well don't be put off if one user gives an unhelpful answer, as you see there have been several proper answers too

Either way the device works pretty much like a pc with linux, so if linux is your thing, you wont go wrong with the N900. If you want to use it like a regular smartphone, you will find a young but rapidly developing platform, and you might just fall in love with linux in the process. You could read this blogpost by the always charming RevdKathy as a reference to what can happen to the curious.