The consensus seems to be that it's overpowered, but having played with it extensively this weekend, I really don't understand that judgment. Not only are all the machines and their components expensive to craft, they also require a ton of Buildcraft power to craft them. Nearly all of AE's blocks require a component that needs to be made in an Assembly Table with gold/diamonds and a rare new ore (quartz). You won't be making any of this stuff until you have a significant infrastructure already in place, making it a mid-end game mod. Unlike EE2, it doesn't give you any methods to generate resources. It doesn’t add any crazy tools or armor… well, it adds a tool that lets you smelt cobble into smooth stone in the environment, but making your floor look pretty at the cost of energy is hardly OP. Nor does it really allow you to condense all your storage into one block. You will need at least three- one block to house the drives which contain your items (ME Drive), one which allows you to access your items (ME Access Terminal), and one which keeps the system powered and acts as the hub of the network (ME controller). If you want to be able to pump items into your ME network and customize your drive storage, you will also need the ME interface and ME preformatter.
Prior to implementing Applied Energistics, I had 6 full silver chests. After implementing AE, I have a 5 block storage network, the contents of which can be accessed through one single block. It requires constant power (IC or BC) to run. So, overpowered? I hardly think so. It is, however, completely awesome. I haven’t gotten to implementing wireless access, automatic crafting, or automated input/ouput yet, due to the cost… but the mod can do all of these things. In the beginning stages, Applied Energistics is just a really expensive way to put your items into drives of various sizes instead of chests of various sizes. You’ll need to invest a significant amount of time, power and resources before you can really reap the benefits. I’d argue that you needn’t bother until your storage room is getting really full, and you have resources to burn. Unless you just love the idea. Which I do.