I was interested in this OS as the successor to BeOS, which some of you might remember almost became the Mac OS. It has been in beta for years. At any rate, there is a nice YouTube review of the most recent verson
here, showing that it has come a long way. It has a lot farther to go before it can be a regular driver for anyone (for example, wifi doesn't seem to work yet), but if you have a half-hour to burn, it's worth watching this review. You can actually get Haiku
here if you want to try it out. You probably wouldn't want to install it though, because, if I remember correctly, the only option is to take over your whole disk. It does have some neat features, though.