I'm a big Java fan, but it seems that Oracle, and before them, Sun, are doing everything in their power to put people off using it.
I've just run one of my applets that I run every day. Today Java came up with a new window saying my version of Java was insecure and "would I like to update it?". I clicked on OK, and it took me to the download page.
"While it's downloading", I thought, "I'll go back to my applet. I don't really have time to install the update today." I didn't bargain for the fact that Oracle had other ideas. Now, every time I go to the page with the applet, it is automatically redirected back to the Java download page. Until I update my Java, Oracle won't let me view any web pages that have an applet. What? Who owns my computer, me or Oracle? This is also Linux I'm running on, so installing isn't just a case of running "install.exe". So goodbye to whatever I thought my job was, Oracle has decide that the only thing I can do now is update my Java.
If that doesn't put people off using Java I don't know what will. I like Java (the language) and use it for almost all my programming, but I wouldn't use it for applets unless you held a gun to my head.
tl;dr - Don't use Java for applets unless you want to lose control of your own computer.