It looks like they have a working keyword search facility, and give you control over price. So they're at least worth of consideration.
There's a critical relationship between how much work it is to upload, versus the chances of actually selling anything, and the responsibilities they take on. Society6, for example, makes it incredibly tedious to submit images. But Fine Art America is a pretty smooth submission process.
Could some of you already using ArtPal comment on this? Do they read the IPTC keywords, for example? Do they handle refunds and returns?