I just wish Microsoft (or anyone, really) made mechanical keyboard with Natural layout.

That would be The Greatest Keyboard Ever Made.

what about the kinesis advantage? http://www.kinesis-ergo.com/advantage.htm

I've got the unicomp 122 that I use at work, and the HHKB Pro Silence∂ that I use at home.

I only got the 122 because they were out of stock of of all the Classic and Space Saver when I was ordering, and truth be told I can't think of any intrinsic advantages that the 122 brings. I do love the layout of the arrow keys (with Home in their middle), but the singe best feature of the board is the BS switches.

Back when I bought mine there were a few more configuration options for the 122, one where the additional F keys (13 - 14) would send a "normal" F13 signal, and one where it sends shift + the F key below it. For example, F13 would send Shift-F1. Seeing how unicomp does not give you options any more, you might want to check what the default is.

Also, if you like the Natural, you might be in to ergo boards? You might like the Truly Ergonimic[1] with MX browns. Watch out of the placement of the important programming keys though, since they are a bit off (~ [ ] { } ; : / \ etc.)

1: https://secure.trulyergonomic.com/

Microsoft would win the game and take the princess home if they just sawed off the damn numpad off either the Natural 4000 or even better the black Natural Elite.

I suspect it depends how the keys feel for you. My advice would be go for the sun, they feel a lot nicer, so much lighter and less effort to type anyone. But I'm speaking as someone who loathes and detests the Model M that so many adore.