Is there a need for ND filters if you bracket your exposures and use photoshop to blend in the correct exposures? I took a course at Maine Multimedia this summer and my instructor said she quit using ND graduated filters and used photoshop with multiple exposures.
Part of the answer is what you enjoy doing. For me I enjoy getting the exposure correct when I take the picture, for others they enjoy doing it in post processing. I am doing more post processing than I used to do, and recently purchased Photoshop. I suspect I'll end up doing some filter effects in Photoshop once I know how but I don't think it will end up replacing my filters since I like to do it in the field.
Personally I have the Lee system:
1x Foundation kit
1x Upgrade kit
**the above two together are equivalent to the Professional kit**
1x each of .6 / .9 Soft Edge ND
1x each of .6 / .9 Hard Edge ND
1x Big Stopper
1x Filter pouch
1x Singh Ray LB Warming Circular Polarizer (fits in the Lee holder)
Yes it is costly but I am happy with the pictures I can produce in the field.