I would say it is highly scalable. Anyone in our business can easily setup their own TeamCity server and assign resources to it. We also have the ability to add multiple agents. In this respect, it is horizontally scalable. 

The whole IT department is using TeamCity. That's 40 to 50 people, approximately. Every dev and every DevOps person is using TeamCity.

At the Enterprise licensing level, there are no limits to the number of, or complexity of the build configurations that can be set up.

The solution is scalable. If an organization needs to expand it, it's possible to do so.

Currently, we have 10-12 users on the solution. These include the creative design team, software engineers, and project managers.

It's easy to scale, but this is on RDS, so you can scale it up and down. I don't think we purchased the scaling features, but they do have scalability. All of our developers are using it, so more than a hundred.

For our usage, it has scaled well to our needs.

Not at all. In fact it was so stable we were able to add and create our own virtual environments each time we needed to deploy. This meant that each user had their own virtual environment, meaning nothing ever got overwritten.

It would be ideal if agents could scale up on demand using a private cloud. The functionality is there for Amazon.

When it comes to plans to increase usage, this depends on the company and the user developer.

No issues enquired.

No issues encountered.

No issues with scalability. When we needed more agents, we simply used pre-configured machines and quickly installed the agent on them.

No issues encountered.

It's working perfectly with multiple projects running continuously on five build agents.

There have been times when making copies of a project has caused major stability issues, especially when you have nested project structure based off of different build configuration templates.

I have encountered some issues using large number of agents, and using git.

No issues encountered.

You have to clean up old projects, otherwise the load on the server increases with increase in size of projects.

No, adding new build agents were enough.

We're not a big company, so we don't need to scale in a big way. It is possible to partly scale by adding multiple agents within the license. It would be quite easy to do this if you need to.