If news of last weeks was Firefox 3, this week, for devs anyway, is Subversion 1.5.
Big new feature is Merge tracking which should significantly ease use of branching/merging.
Upgrade should be easy. Upgrade your clients first, those will upgrade working copies automatically. The upgrade the server, which will run on v1.4 repository until you manually upgrade it. Some new features will not be available just using new server, you'll have to upgrade repositories too. This is not done automatically, so v1.4 clients can access it. Once you are read, simply run "svnadmin upgrade" and you are done.
For more information I suggest you read through Subversion 1.5 Release Notes.
Right now, Windows binaries by Tigris or CollabNet are not available yet, will have to wait few more days. VisualSVN server 1.5 is available. I use Tigris binaries, so I'll wait few more days before upgrading both home and work servers.
Also, all clients where upgraded. I use TortoiseSVN and VisualSVN so don't forget to upgrade those too..