You do have to remove the MacBook from the dock if you need to access the power button, but I rely on sleep and restart and avoid powering it off, altogether. The SD card slot is also blocked but I have an external reader plugged in via USB. Assembling the HengeDock is a little tricky because it's basically molded plastic and metal but all of the electrical connectivity comes from the included cables that must be screwed into place using the included Allen wrench. You provide your own magnetic power supply... I picked up a spare on eBay so I can travel with one and not have to disconnect the docked one. There is a much more expensive alternative, called BookEndz but it's a lot pricier ($200+) but it does allow you to use the screen which might be a plus. Since my MacBook is a 13" model, it wasn't worth it to me. I'd rather use the 23" LCD screen.
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