Model Name: MacBook Air Model Identifier: MacBookAir4,2 Processor Name: Intel Core i7 Processor Speed: 1.8 GHz
Spotlight is re-indexing after the upgrade, which means it's busy all the time, impacting performance and battery life. Never try to judge the performance or battery impact of any major OS X upgrade until the machine has been turned on but idle for at least a week, to give time for the re-indexing to complete.