I considered using it, tried registering but had some issues. Tried reaching out to them but it seems like there is absolutely no way to contact them (other than their twitter, which looks somewhat abandoned).
This made me pretty suspicious, but especially since https://keybase.io/support is just another user claiming to be Keybase support. That's a huge red flag in my book, more so for a security product.
I don't know, but for me this didn't really inspire much confidence.