I traded for a couple. Not that I regret the trade per se, but they are some of the cheapest keycap I have ever seen. Paper thin, flimsy pad printed things and they have a weird profile... not quite Cherry, not DCS, not OEM. I do like the color of the green one for sure, and the way the logo is placed. It's just too bad they didn't take a little more effort in the production, and yes I do realize they were a free promo item.
TLDR, they look cool, but I would say they are not worth more than $1 in any case, even for a big nvidia fan.