Some early adopters of ArcGIS 10.2.1 are reporting some problems. If you can wait, I would stick with 10.2 until a service pack is released for 10.2.1. Here are some comments that I have read in emails:
Sarasota County – Install the full release in a development environment first. Sarasota County GIS experienced difficulties with License Manager (port related), Web Adaptor (must remove existing arcgis site if you want to update it as arcgis again), Server (system and utilities tools have display touchy behavior changes if you want them hosted on say your GpCluster server(s). We are still working to move certain server tools such as Printing off of our mapCluster.
Merced County – Read the version notes and see if anything helps. If you don’t see a benefit then don’t upgrade. I am testing it on a my machine but I’ve already had issues with Model Builder Models acting differently. The geoprocessing tool works differently and will need to be upgraded in each of your models. I for one will not be updating server to 10.2.1 after hearing the news from Florida. I already did not plan on upgrading because this .1 release does not improve anything for my organization.
If you have installed 10.2.1, please add a comment so we all can learn from you!