As just a day-to-day computer for software development, how does it work out? Can it run Firefox/Chromium just fine? What sort of issues have you had?

I've got a couple of Novenas. It's good for development except for web-browsing; for whatever reason firefox and chromium are both pretty sluggish on it. Everything else seems fine; I suspect that it's mostly down to video drivers, which are still somewhat in a state of flux (but getting better).

I'm skeptical about whether the video drivers are the culprit for poor web browsing performance. Yes, there's WebGL, but do Firefox and Chromium depend that critically on OpenGL for rendering ordinary web pages?

Yeah, Novena will be much more usable once the etnaviv drivers are ready.