Hard to quantify "worth it." If you have a relatively stock valvetrain, they don't really do much other than reduce guide wear just a trace. If you have a mondo-lift, gonzo-RPM engine, they maintain geometry better because they don't flex and don't shift around a lot. They also reduce oil temperatures a little bit. The amount of friction reduction isn't worth talking about.
I don't have gonzo-RPM engines any more, but I run full rollers on all of my V8s. There's no real need for them, but I like to envision a reduction in guide wear over time.
Oh, they do make just a little more noise than the stock stamped steel rockers.