Ask HN: How do you easily manage multiple remote servers?

I manage a lot of VPS servers (Linode, Digital Ocean) for work. At first, it was no problem to just SSH in and do maintenance, package upgrades, manage iptables, etc, but I don't find that this scales well past 10+ or so servers (now have upwards of 20).

I'm aware that there are commercial products available, like Parallels, and Canonical's Landscape. However, only some of my servers are running Ubuntu, so that rules out Landscape, and in my limited understanding, running a command panel like Parallels really increases the attack surface on my servers.

Currently I use terminator with broadcasting to simultaneously type on multiple terminals. Are there better options? What tools would you recommend?