Great.
Never laggy unless you don't know what you're doing. People aren't sure how to run the servers correctly because the servers are too easy to make! They dont know what they're doing and cram 100 plugins into a server with 1GB of ram. But for just $5/month you can get an external plan and host it yourself on your own ram lag-free and it's completely fine. Plus, the free plan is good too, it can be optimized easily.