It is sort of the IC2 of the RF ecosystem, but it's a lot less of a resource grind than IC2 often ends up being. I really like Mekanism's models and way of thinking about things, but be aware that its default configs give it RF generation and consumption, weapon damage, and armor values and enchantability that are well beyond that of most other mods. Unless you are just going to play Mekanism, you may want to consider toning its configs down a bit. The Digital Miner in particular does far more with far greater efficiency any other automated miner, and there is very little you can do to mitigate how insanely effective it is. But if you are not too concerned with ideas of pace or balance, Mekanism is really a ton of fun. xyzzy75 covered most of the main points. I would also mention the Fluidic Plenisher, which is similar in concept to Buildcraft's Flood Gate, and the Seismic Vibrator and Reader, loosely based on some real world technology, which helps you assess the ore and spatial composition of a chunk. And yeah, the I/O setup for machines might seem a little weird at first, but there's some good discussion of how colors and faces work on Youtube. For the longest time, I thought it was necessary to use Mekanism's Configurator tool to configure machine sides, and didn't quite understand the color coding system, but it works a bit like Thermal Expansion in that the machine's slots in the GUI each have an assigned color, and you can select which face of the machine block associates with that color.
