I own the A1 & F1 and they're two of my favorite fixed blade outdoor knives. $139.99 is not a must have killer deal for the S1 w/Zytel for me however. It can be had with any diligent searching for less than $125 shipped/no tax with the same Zytel sheath (...and no, it's not from amazon). Had Massdrop come up with the S1 with the leather sheath for around $150 to $175 I'd be all over it. I might come back to it if they don't sell the 100 they agreed to at this time but I'm not jumping in with both feet right now.
On a side note; knocking the knife because of the sheath it comes with is bogus. Fallkniven makes one hell of a knife! But when you pay the bare bones price for a good to excellent fixed blade knife, you get a bare bones crappy sheath. You just do. Deal with it or pay more and get Kydex or Leather, period!
My Beckers at least came with ballistic nylon and while they still leave some to be desired, they're still better than plastic, zytel, grn, or any other merchandising name knife manufacturers want to plaster on a 2 dollar plastic knife "carrier/holder"
My Condor Bushlore I think I paid less than 50 bucks for 5 years ago is the total exception. It's a great small bush knife but the solid leather sheath it came with is worth the price alone and I figure I got the knife for free.
For the $139.99 you're buying the S1 for just shut up about the sheath, throw it out when you get it and buy a good aftermarket one worthy of your quality knife.