If you are monitoring the posts in this forum or the Product Managers' blog, you probably have noticed that PI Web Services 2012 CTP is released. I think this is a great version of PI Web Services to try out because of the new methods to search for PI AF contents like Elements and Element Templates and Event Frames!!
Something that I'd like to share about my experience in upgrading from the 2010 R3 version of PI Web Services to this CTP version in my test environment. I ran the installation directly over my existing installation. Apparently because of this, the original web.config files is kept, together with the few sample web.config files in the Help folder. With the changes of the endpoints that PI Web Services 2012 CTP introduces, the old web.config would not work. This caused me to be unable to access the updated PISearch.svc endpoint as well as the new PIEventFrames.svc endpoint.
If you are going to download and try out this CTP version in your environment, I would recommend that you un-install the old version before re-installing the new version. And it is probably a good idea to remove any files left over in the PI Web Services install folder after un-installing it before you proceed to install again.
If you have already upgraded and have a problem accessing endpoints, you can also try to grab the sample web.config file attached to this post.