One of the features that would make FuelPHP 1.6 unique is the introduction of temporal models. Temporal models enable you to determine the state of a model at a point in time rather than the current state. Think of it as a kind of versioning. If you have used a Wiki, you are probably aware of the ability to view each of the different edits, which is along the lines of walking backward through time to determine how the Wiki page came into its current state of being.
Two other features of FuelPHP’s ORM package are Entity-Attribute-Value (EAV) containers and soft-deletion. EAV containers are used to store attributes about a model when you cannot determine beforehand what those attributes may be, thus removing the rigidity of having a schema. Soft-deletion, as the name implies, is when you do not actually delete data from a table but instead mark a field that indicates that the row should not be displayed. Both the EAV container and soft deletion features are already available in FuelPHP 1.5.