I have used it on 1 server as a test. Worked pretty well, did a few NFS exports from it to other servers. Has been up 546 days, running v4.3 of the OS. No complaints, but I haven't tested it under high load.

I wanna know that too. Never heard of anyone using it in production.

I run a little VPS on DragonFlyBSD that I use for misc hobby projects and personal file hosting. Mostly it runs Postgres. It's quite fast. I had redis running on there as a message queue for a distributed web crawler for a while. I benchmarked it against Arch Linux (which is what I was using on that server before DragonFly) and it was somewhat faster.

HAMMER is a really nice filesystem. It's not one of the fancy COW filesystems (HAMMER2 is, though), but it still has built-in versioning and snapshots and a host of other features. It's great for storing personal projects on.

It's also rock solid and easy to tinker with. I've recompiled my kernel several times with various configs and patches. It is probably the easiest production-ready OS to hack around with.

Also #dragonflybsd on efnet is super helpful.