I've been using them for the last ~10 months or so to run http://PhoenixOnRails.com. Gigalixir have been 100% reliable for me so far, but it's a low-traffic app - I can't tell you what it's like to run a big app on them at scale.

I don't know who owns them but I do get the impression it's a small team. Hasn't been an issue for me so far. Their customer service has been very helpful and responsive on the rare occasions I've needed to contact them