FreeBSD is just fine for web development, and it runs great on VirtualBox if you want to try it. PC-BSD (the "Desktop" edition of FreeBSD) has live CDs and pre-installed VirtualBox and VMware images if you want to give it a try:

http://www.pcbsd.org/en/download.html

Where FreeBSD really shines though, is web deployment -- i.e, it's an awesome platform to deploy your webapps on once they're ready.