The best thing about it is that it is boring, completely predictable outside of hardware faults, and dependable. If you know how to competently manage it, which isn't hard, it is a rock.
Also nice is that FreeBSD isn't involved in vendor tugs-of-war that result in the constant stream of bullshit changes* - the network config format doesn't change every version, people aren't playing political games with init, etc. All of which mean far fewer goofy make-work surprises.
And the quality of their releases is still very high. I consider them one of top open source projects, period, in terms of qualities others should emulate for better results.
As with anything, it isn't for everything. If you need the latest version of whatever is trendy this month, you should run Linux. But if your use case benefits from stability and ease of administration, FreeBSD rocks.
* What is bullshit in my environment may not be in yours, etc.