Great question, Jim... and a tough one to answer. As a life-long cog in other people's machines, I think I might be able to give some insight, though.
I have worked for the US government, huge companies of tens of thousands of employees, 2-man consultancies, startups, VC-funded dotcoms, publishers, military contractors, and just about everything in between.
An employee needs to know that they are making a difference, and that it is appreciated. Generally speaking, I think that has more to do with "the little stuff" than with a big annual bonus.
For example, if a great worker sits at their desk every day, all day, offer them a really nice chair. This will make a material difference to their work experience every single day, and will remind them that they are valued.
A bonus may give someone a momentary spike in their happiness quotient, but that chair will make an immediate impression as well as raise their baseline happiness level over time.
Does that give you some insight?

