I use this lens alot, since I'm a great fan of widefield photos. This is a decent lens both DX and FX.
Be careful with strong light sources in-front of the lens, since it can capture flares easily. I found that the level of distortion is acceptable, and you can easily correct it (i used to have one distortion correction setting saved for CNX2, which i apply to my pics taken with this lens (no matter if its 15 or 30mm)).
One funny thing: always remove the the lens (so you see the flower shaped built-in) hood when using with FX body, else you are gonna shoot funny circle framed shots.