[wavemachine]

I used Cokin's which were okay but got a terrible magenta colour cast when stacking filters but then that can be corrected in PP.

I tend to bracket shots now, i.e. on a tripod take a shot exposed for the land, then another for the sky and combine them in photoshop using a mask layer and the gradient tool, this is the same effect as a gradient filter but you can deal with objects on the horizon better.