The problem with the DSR is that it is BUYER driven, and the seller has absolutely no control over what the buyer puts down, has no recourse to change what a buyer rates the seller at, and the buyer isn't compelled to put down ANYTHING - even worse for sellers with already slightly low DSR's trying to maintain their "elevated" search status.
For example,our store ships items out always in the next business day, yet our "shipping time" rating has been low in the past. Why? For reasons out of the seller's control - the USPS, the weather, and more importantly, what the buyer thinks is a "reasonable" time. One could argue that this problem could be solved by offering different shipping options, but buyers aren't going to pay for more expensive shipping when they're coming for the best deal they can find, even if it means they'll get their item faster.
The DSR simply exists as a way to force Mr. & Mrs. Smalltime off eBay and only retain the Powersellers and high volume, high profit (for eBay, that is) sellers. It's eBay's excuse for driving people off - "Hey, the buyers have spoken, it's not our issue you can't compete with the bigger sellers" they'll say. What they fail to mention that it is a system designed for the big to get bigger and the small to fail, just like eBay wants it, forging their way to be that "Large South American River" competitor.
I don't mean to sound bitter, but I guess I am. I've been on eBay since it started as a buyer, as an occasional seller, and a store owner, and I've seen the whole system go downhill quick. Very sad indeed.