With the SD slot it would have truly been possible to replace my laptop. I could have loaded a few GBs of MP3s onto a (comparatively) cheap SD card and then loaded them onto the (comparatively) expensive storage based in the Atrix. Of course, this would open the door to confusion of where exactly my data was located at any given point, which may be why this feature was axed at some point. Maybe AT&T told Motorola to kill the extra functionality. Perhaps Motorola deemed it a superfluous addition. Heck, it could be that an engineering problem simply made it unfeasible to implement it. I watched a disassembly video of the Laptop Dock just earlier and noted that something does exist behind the plastic void where the SD slot should have been, hidden underneath what looks like a radio shield.
Fact is, the SD reader never made an appearance, yet the marketing doesn't appear to have been properly updated to reflect this change. Odd.