Seen a couple but not in person. They are such underrated fish ... I want to hear about our members who have kept them. I know for a fact that there are 3 members here that have kept them before.
I've seen one once in the LFS near me when it seemed like they went on a little spree buying some really rare oddballs (at the same time they had 2 arapaimas in stock). It lasted about a day or two in the display tank before someone bought it. It was probably about 6 inches long and really cool to watch. I considered picking it up but wanted to wait a few days to see if it ate at the store and by that time it was already purchased.