With RPL - the "IPv6 Routing Protocol for Low-power Lossy Networks" - having been published as a Proposed Standard after a ~2-year development cycle, this document presents an evaluation of the resulting protocol, of its applicability, and of its limits. The documents presents a selection of observations of the protocol characteristics, exposes experiences acquired when producing various prototype implementations of RPL, and presents results obtained from testing this protocol - by way of network simulations, in network testbeds and in deployments. The document aims at providing a better understanding of possible weaknesses and limits of RPL, notably the possible directions that further protocol developments should explore, in order to address these.