On a PC environment when you've got multiple browser windows open, IRC, email client, etc. getting constrained for IOPS is easier than expected.
Generally, I would say that machine would only be IO bound if it had so little memory it was constantly paging.
Those things once loaded are NOT doing heavy disk IO. Heavy disk IO would be thrashing in all likelihood.
So you add more RAM. You'd be amazed how many "IO" problems can be fixed with eliminating the IO in the first place by adding RAM.