I have just upgraded this site with the latest WordPress version. So far all is working, plugins seem to be happy and my custom theme still looks the same. Before you hit the upgrade buttom, please ensure you have made a backup of your site and database.
For more information on the latest version, WordPress has a page with a video that explains it all.
For those of you who have upgraded, what do you think? Like the new features?
Is there any reason not to upgrade ?
One reason you might want to delay upgrading is a compatibility problem with a plugin. That is why you should backup, in case it all goes horribly wrong!