Their filesystem is interesting but what I find impressive is they're at like a linux level of performance despite having a team of like 10 people because of the way they approached concurrency. I believe they spawned out of dillon disagreeing with freebsd's approach, and it's beautiful to me that they're competitive with linux despite not having a huge team of people polishing it.

I also want to say that Matthew Dillon is brilliant and a wonderful person. I played with dragonflybsd on my laptop for a while and hung out in the IRC, and he was always around and willing to help. I found a couple legitimate bugs and he had non-trivial patches up for me in like an hour.

Their networking stuff is very cool too, I can't really remember the details once, but I remember seeing an article about high performance networking that explained why you wanted to avoid the linux kernel so that you could do x,y and z yourself, and dillon explained that dragonfly kernel just does all that stuff itself.

I wish it got more use because there's so much potential there, but it's quite a chicken and the egg problem, and honestly I feel like the BSDs are kind of doomed unless they add apis that support linux containers.