This ^^, whole post in fact.

You also want to check wifi, bluetooth, GPS, camera, flash and battery drainage (either via Powertop or leaving it uncharged for a day or two).

If you want the keyboard, it's in good working order and it's cheap enough, it's a great buy IMHO. The only thing I'm aware of that is better is a Samsung Note 2. These are going for $500+ on eBay so $120 for a N900 is a real bargain. You shouldn't pay more than $150.

Jolla is bringing a high end phone around $700 estimated this quarter which will run a new version of MeeGo.