For me 10.9.3 is a keeper. On my 2012 rmbp, with 10.9.0 and 10.9.1 the UI was very laggy and battery life was miserable (3 hours 30 whilst editing a Word document). Despite multiple clean installs, I never managed to get rid of those symptoms (even with a "pristine" system). 10.9.2 partially addressed and mitigated these issues, but 10.9.3 is absolutely spot on. There isn't a trace of UI or gesture lag to be seen anywhere and the battery usually lasts close to 7 hours for most of my routine tasks.