Every Western expat's least favorite word. It means "God willing" and if you're living in the Middle East, you will hear it a lot.
It's definitely an adjustment to hear Insh'Allah in reference to anything future tense. It's like how we'd say "Hopefully" before something we want to happen, except Insh'Allah is all the time. It's especially annoying when you get the impression that it really means, "Yeah yeah, I'll get to it when I get to it." You can let it drive you crazy, or you can add it to your own vocabulary.
In an effort to fully embrace the Insh'Allah expat lifestyle, I embroidered a friend a little bit of Insh'Allah to keep nearby in her kitchen.