It really depends on your expectations and budget.
I did programming, image/movie editing, and some CAD modeling on an older (early 07) Core 2 Duo Macbook with 2GB RAM.
In addition to some average movie editing (never more than 10 minutes), and editing 50+MB Photoshop files, I was able to render and rotate fairly complex models of an automobile rotisserie in real time with no issues. I only really got bogged down when I tried importing extremely complex 3D models such as an entire automobile. I'm guessing that has to do a lot with the non-MB's poor OpenGL performance.
My point is that you can certainly shave some time off here and there with a more expensive model, but unless you absolutely need (and can afford) the cutting edge you'll be happy with a MB.
I like the MB so much I'm upgrading to a new 2.0GHz Macbook with 4GB. I was going to go for 2.2, but I really don't need the drives and 200MHz and I'd rather have quadruple the ram and still save a $100.
As an aside, it would have been nice to get an Air. I was so disappointed when I heard the specs - especially the default PATA drive. If they can squish a little bit more into by this Fall, I'll be first in line.