I have Das Keyboard mechanical keyboards on all of my home systems. I have spinal nerve damage that reduces sensation in some of my fingers. The positive tactile feel of the switches and the clicky sounds are very helpful in compensating for the reduced feeling in my fingers.
I have a Das Keyboard as well as a Unicomp Model M. Unfortunately, the Unicomp needs to go in for repair. In terms of overall size, I like Das Keyboard better, but I haven't tried the smaller Unicomps. That said, I think the tactile feedback of the Unicomps is much closer to the Model M than the Das Keyboard.
Both are far superior to many cheap keyboards.
I only wish Unicomp or Das Keyboard came in a bluetooth version. The Das Keyboard using 2 USB ports is a tad bogus.
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.