I've been using debian vservers in the past, and now lxc. RedHat 7 and its LXC integration is amazing. I use KVM as my hypervisor of choice, so I'm already using virtual machine manager, so now I can manage my LXC hosts with VMM, its really a nice touch.
What really interests me is LXD. LXC containers in a real isolated container that I can just move. Right now, I'm stuck to zipping and moving LXC's directories if I want to move them. I tend to use OS containers stripped down, because I want app/tcp/ssh/nrpe installed, so I can make sure the service is alarmed, and I use ssh for remote management.
Docker tends to be aimed at enterprise usage, if you have lots of single applications appliances, you can roll out and tear down, docker is a great idea.
That is a different use case, so I don't need docker, but docker is built on LXC, so I get that added benefits from support from Redhat. (and Centos7 support)
I'm running an IT shop, so my servers run for years, and I need to be able to manage, and support them. LXC containers is the perfect middle ground for me. LXD is the only thing I'm missing, moving file based containers.
So, I'm happy docker is pushing technology, because the stack it runs on is also benefiting from it.
BTW, I wish Redhat would support LXC VM's on its REHV (ovirt) platform, then I could consolidate even more VM's into single VM's. Guests with bridges with macs are filtered due to IP spoofing rules. Kinda silly when RedHat pushes LXC on 7, but doesn't test LXC on its Visualization platform.