> If a design isn't great is isn't because the computer was too slow, or didn't have enough ram, or the designer didn't own the right plug in.  

How would we know? Production houses don't normally talk about the budget and scheduling for projects cuz that's proprietary info. I've seen good ideas fail because of poor execution. If production doesn't have the resources to carry out a brilliant idea, it's not going to work.

I think a lot of design is trial and error. It's experimenting. What happens if I do this? What if I do this? When a tool is slow, it limits the number of iterations you can go through before your deadline.

I wouldn't ever say that a bad designer can produce good work given sufficient tools and a burly workstation, but a the lack of those same things can certainly hinder a good designer. Unless all your clients are into swiss minimalism, I think speed is a big deal.

Also. Working with a slow tool just isn't fun.