I've been using Filter Forge going on two years now. I love the hell out of this program, I really do.
I found several things fr om Photoshop that I really miss in Filter Forge.
Starting with the smaller ones:
1. Ability to raise/lower numbers using keys, when number is selected. Like in Photoshop.
2. Ability to easily copy color information (Maybe a swatch tool?)
Now a big one that would be a feature I couldn't wait to pay for for Filter Forge 3:
Let us combine diferrent filters in a studio wh ere filters are layers. This could make Filter Forge SO much more useful. Each filter could be prerendered. It would just be great to be able to combine diferrent filters as a whole with blending options. Ooooooohhh....