Update 2002-06-05: Be, Inc changed their strategy a long time ago so that their OS is targetted at embedded devices. In any case, I'm much more interested now in the idea of Java being the solution to the OS lock-in problem. The BeOS was a great OS, but they never had a Java interpreter, so that was a problem.
On January 1, 1999 I installed BeOS R4. My initial impressions are highly favorable. It installed on a second partition quickly and without any problems at all. It's very speedy and responsive. WinNT 4 is extremely sluggish when compared to the BeOS (running on the same machine). The BeOS boots in roughly 15 seconds while WinNT 4 takes about 3 minutes 45 seconds. All BeOS applications load in less than a second. Few WinNT applications beyond notepad and calc can claim that.
Programming for the BeOS is far easier than programming for Windows. The C++ API is quite beautiful (especially when compared to the kludgy clunky API for Windows).