Currently @mgmartel's work on #138 was somehow "lost" in merge conflicts into master. Over the last few days, I've been working on replaying these commits on-top of the current dev branch to integrate the features of both the iterators (which better harmonize with the WP loop) and removing excess code from timber.php. The result is located in:

https://github.com/jarednova/timber/tree/iterators

... however, there are a few outstanding issues before this can be merged with master:

• Must pass the test for post previews (that is, viewing the contents of a post before it is "published" ) fails. This is TimberTest::testGetPostPreview
• Remove redundant function calls to simplify the classes for Timber and TimberPostGetter. I'm comfortable breaking backwards compatibility in the rare situation when someone was accessing a function like get_posts_from_array_of_ids directly. Even as an expert-level Timber developer (yeah, I said it), I never used these methods directly outside of unit tests.