Permission 3.1.6 is inactive now, but i still use that plugin until this time. The reason is that plugin is simple and really easy to use. The in-game commands are structured really well. I think its the best permission plugin. Its just "work" if you know what i mean. Lots of server owners i know still use that permission too. It will be really great if someone take over that plugin and update it to make it compatible with the next craftbukkit builds. If its updated, plugin developers will also make their plugins compatible with 3.1.6. Lots of new plugins didnt support 3.1.6 anymore. And also, some of existing plugins dropped their 3.1.6 support. If someone willing to take over permission 3.1.6, i will 100% suuport and maybe i will donate some money too.