My shop has been using Subversion for a number of years. It is a reliable tool and works well for our team. One area that Subversion could handle better is tracking merge information. Our team is always working on multiple feature branches and merging those changes back into the main line of development. The current merge support works fine (most of the time), but doesn't handle complex situations well.
Subversion 1.5 begins to improve this with "Merge tracking" support. From the Release Notes: Merge tracking means Subversion keeps track of what changes have been merged where. This reduces the overhead involved in maintaining branches, and gives users a way to inquire what changes are merged — or are available to be merged — on different lines of development. Subversion 1.5 adds "foundational" support for merge tracking with more improvements coming in v1.5.1 and beyond.
Besides merge tracking, they've made a number of other changes. Here's the full list:
TortoiseSVN (our favorite SVN client) has also released version 1.5. We're setting up a VM to test our code base on 1.5. Once I've given it a good test drive, I'll post more.