I've played with Haiku in a VM in the past. But what is suggested that I do with the OS? Be a daily driver? Does it fit some niche use case? I have an old netbook, I'd load Haiku on the boot partition, I really would. I'm a sucker for something different (given the evils of Big OS and all), and for the underdog. Hell, I might even contribute if I have something (coding wise) to give. So I load 'er up on the ol' boot…
It's a general-purpose OS. Do whatever you normally do on it. More importantly, it's a learning tool. It's been part of many courses and many rounds of Google Summer of Code. It's an embeddable kernel + OS free of the cancerous GPL, under a permissive MIT licence. It is extremely well documented, well tested, and consistent. Writing drivers for it is very simple. This makes it interesting for education, for-profit de…
What I normally do involves a lot of software that does not run on Haiku. Is there a Citrix receiver for it? Does Cisco make an AnyConnect client? What about LibreOffice? Java? Flash?
I love the idea of Haiku, don't get me wrong. But the question of "what can I do with it" is not answered by "whatever you normally do", especially if (considering your second paragraph) what I normally do does not entail writing device drivers. An OS means nothing without compatible software. Ask anyone who uses Windows Phone.