They're the leader of the SIEM market for fifteen years or so. ArcSight is a very capable product that integrates with many different platforms. It's huge with a lot of moving parts, but nothing can compete with it in terms of capability.
I'm a little concerned that the market is moving around ArcSight. It's a fantastic SIEM, but the recent metrics show that relying too heavily on a SIEM solution isn't protecting us. ArcSight addresses that by integrating with other solutions, but I'd like to see that to be a more central element of it.
We've had no issues with deployment.
It is incredibly stable and road-tested, reasons why it's a market leader.
It's highly scalable. It works in small scenarios as well as the biggest that I can imagine.
Technical support from the vendor has been good. There's a particular challenge with ArcSight not in the technical support, but in the fact that it supports the platform and the integration.
The initial setup is relatively complex because it's not a small solution. It's not only complex to set up, but the interface with business operations is even more complex around scoping, implementing, and running an implementation.
Make sure you tune it to your business and infrastructure, which isn't necessarily part of technical support. It requires some consulting, which is a market challenge of the product.
It's not a one-size-fits-all solution and it isn't sold with the appropriate professional services. So the number one thing with ArcSight is that you have to make sure that you get professional services to help size it for your particular use case, including integrations with your tools, operational model, and security operations.