Well, it boots and runs. It runs BeOS software. I'm supposed to be able to make the WiFi in my netbook work, but I can't find where in the UI one would configure networking. There's an incredibly chintzy little network manager, but it makes the stuff from System 7 look like server configuration.
Since the thing is built on Linux, I assume that the old fashioned methods work. I hope.
As far as speed, it boots on a Celeron 600 lappy in about twenty seconds from the Live CD. Think more like ten if starting from the HD. On my dual-core Atom netbook, we're thinking more... Oh... Five second boot-time? I can't say about stability, since I can't really use it for anything. I need to just put it through its paces running a bunch of crap until it blows up, but I don't think it will. It seems pretty rock-solid. It's a great re-implementation of BeOS in FOSS.
As much as I hate to harp on it, Haiku makes a lot of other FOSS projects look downright lazy. GNUStep is who I'm looking at. Linux+GNUStep could have easily become the FOSS Mac OS X, but the GNUStep devs seem far more interested in creating a panacea for other developers without a clear aim as to what people would run the software on.
Haiku though has in a decade, gone from "big ideas" to a complete product. Haiku and ReactOS really seem to be the caliber of teams that FOSS needs. Hats off to 'em!