Yes, many users including myself feel Linux is smoother, more efficient, and more scalable than Windows. For beginners, I suggest trying Ubuntu Linux (http://www.ubuntu.com/getubuntu/download
) and running from the LiveCD. After burning the ISO image, you can try out Ubuntu booting and running from the LiveCD without needing to install. Or you can install it to your spare laptop. (In fact, you can easily install it for multiple bootup into any working Windows installation. GRUB will automatically assist you to set aside a Linux partition and allow you to choose Windows or Linux on bootup.)
Yes, Linux will run Java. Just download and install the Linux
Java runtime from Sun (http://www.java.com/en/download/manual.jsp
Yes, you can still browse the web, including "just like on Windows"
The default browser for Ubuntu is Firefox which is extremely similar to the Windows version (after all, that's the whole purpose of Mozilla's XUL interface). As well, SRWare Iron/Chrome beta for Linux will be out soon for general public testing, and that works extremely similar on Linux as well.