There is a fresh update for your servers. Around 100 issues fixed since the previous release throughout the different functionality. There are several performance-related fixes for large TeamCity installations and minor improvements in lots of other areas.
You can freely upgrade/downgrade within all the 8.1.x releases, so do not hesitate much if you are already running 8.1.x build.
Just get the build and check usual upgrade instructions if you need a refresh.
In the meantime we are already working on TeamCity 9.0 functionality which will likely to get several long-awaited features implemented. Stay tuned!