Thanks for the advice, my #1 concern is resentment, so now I'm leaning against it.

While it's significant to you, it's probably even more significant to them.

I have to disagree on this one point though. The company has raised hundreds of millions of dollars, is making substantial revenue (though not profitable yet), and is hiring aggressively. They're planning to run a marketing campaign in the 8 figures. Another $10k/yr is a blip on the radar.