Let them change their start time. (They're probably doing that anyway - if you work outside and need sunlight, you're not starting at the same hour in March and June.)
That assumes a tremendous amount of scheduling freedom on the part of the average retail worker or office drone, which I do not believe to be a correct assumption. Business Opens At 8 (or 9) is so ingrained as to be unlikely to change.
Tradespeople - particularly contractors - on the other hand, have a fair degree of freedom to decide when to start work, and they tend to start when the light starts (or shortly before) and stop aroundish the time the light fades. It doesn't really matter to them what the clock says, yet we continue to see arguments that DST is evil because it forces tradies to start at times that don't correspond with the light. To that I say, a) bullshit, b) prove it.
