minor ethical dilemma

Back in early December I bought a gift for someone. The item was greatly enjoyed, but took forever to ship and was therefore late. I bought it through Amazon.com's "marketplace" (3rd parties selling through Amazon.com). Amazon asks people who bought items from the Marketplace to rate the 3rd party merchants so that others know how reliable the company is. I left what I felt was an honest, overall neutral review basically saying "the product is really great, but the delivery took too long."

Yesterday I received an email from said merchant appologizing for my poor experience, and offering to compensate me with a free item of my choice (from a short list) *if* I remove my "negative feedback." So... should I accept the bribe, or let other consumers know the full picture? The email provided a very reasonable explanation for the delay - it was the holiday season, they had received a lot of publicity and were not expecting the huge amount of orders they received.

The company has 1300 3100+ reviews, only 6% of those are "negative." Are they so concerned with their image that they want it to be 0%? How many other companies have artificial ratings because they bribe unhappy customers to retract honest (but negative) reviews? I think if I had had a trully bad experience (like the item never showed up and they didn't give me a refund), no amount of bribery would make me remove that information. But in this case, what happened wasn't that bad, and has a good explanation.

Update: technically, my review is considered "neutral" by Amazon. I was just reading through some of the real "negative" reviews and they tend to be very bitter and angry. I don't think these people would sell out for a $15 gesture. I think the company is probably only trying to appease the 3% of the neutral reviewers.

What to do?