This is a divisive term in the world of real estate.
Some agents will happily represent both the buyer and the seller on a transaction. Some agents are vehemently against it and believe there is no way to adequately and fairly represent both parties. Other agents will only consider it in non-multiple offer situations. Other agents foam at the mouth and bend over backwards to try to find "double-ended deals".
As long as it's allowed, I think it will always be up for debate. But, the most important thing that I always keep in mind is: what's best for the client(s)?