Has the existence of the arm brace changed the way AR15 users might consider them, yes. It has grown exponentially since the determination that they can be shouldered. Thanks for the explanations concerning SBR stamps, transport, etc. It wasn't so obvious before how arbitrary and onerous some of the restrictions are. What a contrast to the carry and use of a pistol - which in this case is a breeze. And in many jurisdictions it's legal to carry them loaded, unlike a rifle which must be cased with ammo separate.
SIG has introduced another model to the lineup, which means they don't see it as stealing sales from the existing model, but adding sales. If that is a reflection on the styling of the first one, fine, if you don't like it, ok. The market is full of dress up stocks, handguards, and grips, and most are sold precisely because somebody doesn't like the hideous looks of Brand X. Taste isn't always a big discriminator in firearm sales, if I am to believe my eyes when I see a bright green and black zebra striped polymer frame on a pistol.
What we have is a gamechanger. What WAS a long wait for a short barreled rifle with extra fees and requirements is NOW a no big deal pistol build. What WAS a restricted and limited item is NOW another AR build genre with no holds barred, literally. Just pick a pistol buffer tube that you are legally comfortable with.
As long as this window of opportunity exists, why penalize yourself with the costs of a stamp, trust, inheritance, transport, and other hassles of an SBR, when the BATF just cut you a huge amount of slack?
Does it mean that someone who would never have bothered to apply for an SBR stamp is now interested? READ THE FORUMS - it's the hottest thing going now, and that's in a declining gun market. Those considering an AR build are waking up and seeing a huge opportunity. An "SBR" - for "free," no waiting or any more hassle other than building to one specific feature - a buffer tube that can't "accept" or be "easily modified" for a rifle stock.
It's about freedom, and this decision is a major surprise during what we thought was an anti gun administration. In just the last few months there are threads popping up in other forums, with a renewed interest in how to build an AR pistol, all because the wrist brace opened the opportunity. If all it takes is a wrist brace with pistol buffer and you save $200, ten months, a trust, transport hassles, etc., there would have to be a seriously compelling reason to endure the hassle. Which hasn't been yet revealed - and never really was.