is a 29er a good fit for a 5'9 height?
I would say it depends on your riding style and the geometry of the specific bike you are looking at.  29'r is definitely not to big for you (I am 5'10" and my 29'rs are just fine).  However, there are reasons that a lot of all mountain, freeride and almost all downhill rigs are still 26".  29'rs are less suited for highly technical riding, but much better suited for cross country and trail riding.  As always, tailor your bicycle choice to your riding style.  

If you are into flowy single track and aren't hitting drops, ripping through rock gardens and generally abusing the landscape with your rig, then 29" is probably a better choice for you (with the right size frame).