I own a 1994 Model M and recently bought the Das Keyboard for Mac, and the Das Keyboard is horrible. The keys wiggle a bit and feel mushy compared to the crisp clack of the Model M. Also the extra usb ports mean needing to use two ports on my MBP which is stupid. I'm still pissed at myself for not returning it when I had the chance.
The second USB port is just for the USB Hub (which is why the connector says "HUB" on it). It is not required for using the Das Keyboard. My Das Keyboard doesn't have any key wiggle or mushiness issues. What type of Cherry MX switches did you buy? You may want to get MX switches with more resistance if you are looking for a feel similar to the Model M.