FreeBSD has almost the same software support as Linux. And Mozilla is not a Linux app; it's a browser evolved from Netscape, and available for virtually every platform.
Since you already have Red Hat 9, I assume you already know about KDE / GNOME. FreeBSD is not designed with beginners in mind, but it is certainly manageable if you already used Linux and Mac OS X. Once FreeBSD is installed, day to day use on the desktop should be comparable to what you're used to on Red Hat, as it uses the same desktop managers.
The not-so-easy part of FreeBSD is the installation, which is menu-based and not graphical. Despite the looks of the Sysinstall interface, the installation is pretty straightforward, and you will get all the necessary instructions as you go on. Also, you get generic KDE / GNOME interfaces instead of the customised Red Hat versions. On the other hand, applications are much less a hassle to install on FreeBSD, because every application available for FreeBSD can be installed from the Sysinstall utility, and you won't get problems like package or repository dependencies that can become growing pains on Linux.
By all means, give it a try. It's not a noob OS, but you can learn a lot about UNIX through FreeBSD (although you don't really need to). If it's really too taxing for you, then you could always try Mandrake Linux. Heck, you can always dual boot between the two.
[ November 04, 2003: Message edited by: Laukev7 ]