Haiku is designed to be a clone of BeOS, a long forgotten operating system produced by the long-defunct Be Inc. BeOS was originally released for a proprietary multimedia system known as the BeBox, but later opened up to both IBM PC compatibles and the Macintosh.
While Alpha 4 was mainly designed to be a bug-fix release, there have been a couple of changes since Alpha 3 (and certainly since I reviewed Alpha 1).
Haiku seems to have fallen into a development slumber. I took these screenshots of Alpha 4.1 back sometime in 2014, and as of this writing (April 5, 2016) there have been no new "stable" releases. I'm not sure what the ultimate fate of the project will be.
Here is the Haiku installer. Seems interesting that they mention the potential instability of creating partitions. Patrition editors have been around for a very long time, so it's natural to think that this wouldn't (or shouldn't) be a huge risk. I can only guess that they're using their own solution for that.
The install process is painless, however I noticed that the LiveCD is rather slow. This is actually a known bug with Haiku, supposedly because it needs to perform "background tasks" to set up the operating environment.
The splash screen has remained unchanged.
The Haiku desktop has remained mostly unchanged from the original BeOS and prior versions of Haiku.
Noticeable right off the bat are a few extra desktop icons, and some "notifcation bar" icons as well. Haiku now includes a few welcome documents locally (instead of internet pages), and also implements WPA/WPA2 wireless networking. Oh, and sound too!
The about page hasn't changed much. Haiku A4 includes better CPU detection and a newer kernel revision with some enhancements and bug fixes.
The menu has remained mostly unchanged from prior versions.