Adobe has announced an update to Lightroom from version 5.0 to 5.2. (There was no 5.1 version.) This update is free to anyone who owns a copy of version 5.0. If you are just purchasing Lightroom, this is the version you will get when you download the software.
There appear to be a number of important bug fixes as well as the usual additional support for new cameras. Adobe has also included a few improvements to existing features, notably the Spot Removal tool. It now has a feather slider to improve blending when using the Clone option as well as better choices for the source selection.
See Laura Shoe's blog entry for an excellent video and written summary of important changes in this release.
What's New in Lightroom 5.2