I have recently had the chance to play again with the 3 BSD's, under the excuse of testing the portability of a piece of software. I was able to install all of them in separate virtual machines under VMWare Server. I'm summarizing my impressions below. Chiefly, I was surprised at the number of (admittedly minor) annoyances that NetBSD gave me (I recall having no such problems a couple of years ago when I first tried this OS).

FreeBSD:

• Most desktop-friendly, easiest to install
• Issues with XFree86 to Xorg transition still cause problems in 6.3 (something the Linux distros have long ago solved)

NetBSD:

• Less friendly installer compared to FreeBSD, but still quite useable
• Make sure to install the text and man sets
• pkg_add doesn't quite work with some mirrors (e.g. ftp.at.netbsd.org) because it insists on using a complex wildcard pattern to look for packages (package-*.t[bg]z). Some FTP servers don't support this pattern, and return no results. Bottom line: pkg_add bash sometimes fails, but pkg_add bash-3.2.25 always works.
• IPv6 seems to be sadly enabled in most applications and for the most part causes only delays and error messages; most annoyingly so with pkg_add
• Furthermore, the community seems to think IPv6 is the best thing since sliced bread. Search for "disable ipv6 netbsd"; you will find mostly unanswered forum messages, or when they are answered, the answer is along the lines "why do you need to do this".
• Under VMWare, you must wait until NetBSD finishes booting up before you can press CTRL+ALT to release the mouse (and do other things in the host OS); otherwise, the console dies.
• Seems easiest to port on an embedded system (and runs on the largest number of platforms)

OpenBSD:

• Somewhat resembles NetBSD
• Least friendly installer ("dumb terminal" style, not even curses-enhanced)
• You must install the xbase set (even if you're not planning on using X) or else most packages won't install later (including bash)
• Default GCC version is the oldest (3.3.5); newer versions are available separately, but seem to come with different features (e.g. the ProPolice stack protector is not enabled)
• Large number of security features that I did not try out