I kept it disabled with my 7100t a long time ago to speed up page loading. But since then, I've always kept it enabled. I think nowadays you will find even many mobile pages are using java and you'll miss out on some features if you disable it. But I can't cite examples.
Java is very useful feature. Mine is disabled, but I visit a few page what require java for better experience, I bookmark them and set Java: Enabled.
Java is slow down browsing, java is plus, its downloaded to your phone, and run it localy..