Good answers already. And just to emphasize two points: Commissions are negotiable (as you know), and customs and practices tend to vary by community.
However, IF, hypothetically, the most common commission rate for your area is 6%, with 3% to each agent, then your agent is already doing you a favor by reducing his commission. Some agents wouldn't do that. Similarly, when representing a buyer, many agents would prefer a 3% commission to a 2.5% commission. That doesn't mean they won't show your property, but they might suggest viewing other properties first.
One thing a lower commission can suggest is that it might be more difficult to deal with a seller, that there may well be glitches and problems with other areas of the transaction. It can also suggest that the seller isn't really all that interested in selling. It certainly can suggest that the seller has less flexibility in price negotiations, and that can be a real deal-killer especially if your home isn't already very attractively priced.
So: Do whatever you wish. Just recognize some of the trade-offs for what is a 1/2% savings on the commission--all of, let's say, $5,000 on a $1 million property.