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
Am I right in thinking the platform got bought a little while ago, and it’s being run by a relatively small outfit?