The keyboard is well built and it feels solid. It's slightly smaller than a Filco and a bit lighter. The USB cable is gold plated.

Keys/Legends are fine apart for the outrageous win8 logo.

In the box were included some extra keys but I think they are part of an initial promotion, it should just come with the control/caps-lock replacement.

There's rubber on the feet, which is a very nice addition.

To my great surprise and pleasure FN+arrow-keys perform home/end/pg.up/pg.down. This is not printed on front of the keys like the other legends for the FN layer. I was considering hacking the 660c with a Teensy to adjust the FN layer, but I must say that it's almost perfect as it is.
Other nice addition is the FN+Q that inverts the FN layer on the ESC key (`~ instead of ESC). When the lock is activated a red LED on the INS key lights up.
INS/DEL keys are slightly too far to the right. The distance between \| and DEL is not standard and forces a longer travel with your hand to reach it (compared to a Filco). This is a negligible annoyance of an otherwise great keyboard. Also the usefulness of the INS key is disputable, but I know people who can't live without it, so...
Topre switches are great. The sound and feel of plate mounted tropres is mesmerizing and a real pleasure to type on. My main board is a Filco with MX Blue and I love loud and clicky boards, but this Leopold I'm afraid will dethronize my beloved Filco.
There's a dip switch to make some fine tuning to the layout. Apart from the control/caps switch, you can also invert win/alt (useful for mac users) and place the FN to the left in lieu of the win key.
What I really would have liked is FN+backspace = DEL... Also FN instead of capslock would be nice... but it's just a matter of personal preference. I think I'll soon open it and see how hard it is to hack. With very little additions to the FN layer this could be easily one of my preferred keyboards.
If you have any question don't hesitate to ask.