I've had my 15" rMBP for about 7 months. It has worked very well for me, and I have had very few issues up until this point. I've backed up all my data, and clean restored my Mac to the new OS X Mavericks. With this new upgrade, not only did I get very few new features, but tons of new issues. Beach ball constantly appearing, system hangs, applications constantly crashing, and generally poor performance. Most tasks requiring heavy graphics usage have been very choppy on Mavericks, compared to running smooth as butter on Mountain Lion. My question is, has anyone else been having a significant performance decrease with Mavericks? It seems like the cons far outweigh the pros of this update.