Developers now will be able to create signed applets and to configure their systems to allow those applets greater freedom. We distribute a tool called appletviewer that developers can use to help them create and test their signed applets. Down the road, we expect that Java-enabled browsers will support Java digital signatures, but I don't know the dates for when that will be available to end users. We're working very closely with our Java licensees to help make that happen. Any time you have a system as complex as the JDK and Java VM, there will almost certainly be bugs.
Every bug introduces potential security holes.
Based on the history of bug discovery in earlier versions of the JDK, it is unlikely that the most recent bug in the javakey implementation is the only one.