If you happen to find some example code that elegantly solves your exact problem, check which version of Ember it uses. Sometimes that perfect example is a few versions ahead and will do absolutely nothing for you. If you’re smarter than I am and check the version number right away, you can save yourself a good half hour of cleaning, rebuilding, and cursing.
On the upside, if you need to iterate over a map with {{#each foo in bar}}, you can hammer together a workaround using Ember.keys(map) – but again, only if you have the right version of ember. Ember.keys() was deprecated in 1.13, use Object.keys() instead if your version of Ember is later than 1.13.