To access the battery chamber you have to unscrew two small screws. This worries me because you have to put in fresh batteries like every few hours. The appetite this hub has for batteries is enough to make this simply unusable. Don't make the mistake of using any non-recharchable batteries even if you're excited to put things in action for the very first time. You're giving those batteries an hour-long death sentence.) At any rate, those screws are going to wear out, never mind they're inconvenient. It's LEGO! It should secure shut with studs or snaps! Especially considering how frequently you'll have to change batteries!
Next up is the huge limitation that you only get two accessories. No more daisy-chaining to bedazzle your project with lights. I'm building a train and if it uses the older PF which they're trying to phase out, I can have two motors and several lights off of one battery box AND I won't have to change the batteries in an hour. With the new Powered UP components, I have to choose between two motors OR a motor and one light. I can't even daisy-chain more lights to light up the trailing cars!
Lastly we have the controls. If you're using one of the linear motors (rather than the train motor), and you have the remote control unit, you get binary output from the motor (it's either on or it's off) with no modulation (no regulating the speed). Also, you have to sit there and hold the button down, the moment you lift your finger the motor will stop. So it sucks for trains.
You can get more fine control if you download the app to use, but be prepared to spend quite a long time just trying to figure out how to do the most basic things in the app with little success. There's no documentation and very little guidance on the Internet to help you utilize the software. I'm an IT Engineer with programming experience, I figure software out for a living, and this one is a challenge! The programming itself is simple enough, but the UI around the actual programming is as clear as mud. If you try the "controller" option which should simply just simulate a controller, well one of the two choices won't actually do anything so even that wasn't 100% "plug and play" (I had the misfortune of trying the one that won't do anything first).
Even the cords seem like a poor choice, carrying on from the ribbon cables of the PF world but seemingly even more rigid this time. So if you're building a project with any articulation, the PU component cables are REALLY working against you. By being flat ribbon cables they'll only flex in one plane, and they're rigid enough that they're more likely to move your project's joints than your joints are likely to move them. They pose a significant engineering challenge (and restriction) for my train.
The one positive (and reason I tried the new components) is not needing the IR module (which means I don't have to figure out how to build it into my project, plus it means fewer cords). But despite that huge gain, I'm at a loss to compensate for all of the other shortcomings. The battery life is really the big one. Even if I use rechargables, having to change them so frequently (basically every time you want to run your devices) is just not going to cut it. Well oh and I want two motors plus lights. Can't have it with Powered Up, can have it with Power Functions. Why is that, LEGO? Why have you added that limitation?
At any rate, I'm pretty dissatisfied with their design choices and their execution of the new PU components and pretty sure I'll be returning everything and going back to PF (while I still can)."