Generally, those from the engineering community sneer at the MakerBot and the RepRap. Just listen for the word "tolerances."
Now, they're totally right: the home printers have a significantly lower resolution than the professional ones. But unless you're making professional grade parts, you probably don't care, and they use the same materials. (I'm assuming you're making the comparison to other FDM machines.)
Assuming the tolerances for the cheap 3D printers will improve, isn't this a classic case of disruption we are seeing here?
Sure they aren't great enough for everything yet, but there has to be things you can create even with the cheap bots that are good enough to be useful.
I expect it to be similar to what happened with the printing press and computers in that you'll be able to download (/pirate) actual objects. The revolution will be huge.
The best machine gun in Mass Effect 2 has "Fabrication Rights Management" technology which prevents you from printing one for each member of your team. I doubt real-world engineers for companies whose products would be most affected by downloadability are too far behind.
Now, they're totally right: the home printers have a significantly lower resolution than the professional ones. But unless you're making professional grade parts, you probably don't care, and they use the same materials. (I'm assuming you're making the comparison to other FDM machines.)