What do you like best?
The control you have over your containers is really cool.
As an admin you can jump into a running container as root with one command.
Startup times for the containers is very fast.
When used in conjunction with Proxmox OpenVZ can compete with most of the big boys out there right now.
What do you dislike?
Well there a few things.
The documentation is very comprehensive but it can still be a struggle to find guides for your specific version.
I find particularly network config and firewall config is always an issue.
Network interfaces seem to disappear from time to time randomly.
Recommendations to others considering the product
Its a steep learning curve with a lot of config.
Weigh up your options, if you are relying heavily on Linux based infrastructure in the back end then it may be a good fit.
If your a windows only house then i would stick with Hyper-V
What business problems are you solving with the product? What benefits have you realized?
All of our in house virtualization is now done through Proxmox using OpenVZ templates.