Paid in gear: the ethics of reviewing free camping equipment

I got a high end sleeping bag from a company to test out last fall. Used it on a weekend hike in the mountains. The zipper always snagged on the fabric, making it hard to open at night. After I washed it once, the down bunched up in weird places. The brand emailed me a couple times, hinting I should focus on the positive stuff. I was torn between being truthful and feeling grateful for the free item. I posted a full review with both pros and cons, but they cut me off from more gear. It shows how free stuff can mess with honest opinions.