When I stop tracking, go to the screen where you set the Grain size, click on a big grain size (not sure if that's important) and press Next BEFORE it has time to finish applying the blur (for the preview), it gets stuck with a full progress bar (with a rotating "Progress"). I call it "small bug" because "cancel" works, so the application is still perfectly responsive, it will just do nothing if you leave it like that. This is with alpha 315 and 316 on OS X.
Also, I really think you are being too harsh about the alpha designation. I know that originally going to beta meant feature completeness, but nowadays it just means "reasonable stability" (google did this to the max by their "perpetual beta" software which kept getting/changing functionality) and you are way past that point. The ST alpha version does not feel "alpha" in any way and the name might be scaring more users than you should into staying with 1.3