Well, I got my r419b on Saturday and have put in my five rounds (spread over my three local courses) already. Here are thoughts I shared with Vibram through the tester page.
R419b:
-Very understable, but very controllable
-Very shallow rim. It felt fine to me, but may bother those with bigger hands.
-Comparable to a Mamba, just a little faster/speed stable
-Thrown flat, it would start tracking right and keep turning, never fighting back. But it would not cut over into a roller if it was given enough height.
-Thrown with a slight hyzer, it would pop up to flat quickly and then slowly track right late in it's flight. A very useful turnover line!
-Thrown with a deep hyzer angle, it would pop up later in it's flight, fly straight, and sometimes even fade out.
-Thrown on an anhyzer, it turned and burned quickly. I am not one who throws many rollers, but I could see this being a decent roller disc out of the box for players with slower arm speed.
-A very workable disc for someone with slower arm speed/less snap who has a good understanding/control of hyzer angles.
-Very, very good glide. Even when thrown on low lines.
-Loves to be powered down. Adjusting arm speed and hyzer angles can shape some great lines, including a beautiful, easy sweeping hyzer that glides for days.
-Finicky in the wind. Handled cross winds better than I expected (especially left to right; I expected the r419b to be pushed hard to the right and into the ground but it just tracked slowly right with the wind), but turned and burned in a good headwind like I expected. LOVES a tailwind, this thing can float for days thrown on a hyzer/hyzer-flip line with a tailwind.
-At the end of back to back rounds, I could still bomb this disc, despite some fatigue. That's a great distance driver to have in the bag, for those long tourneys/leagues/etc in the dog days of summer.
-My r419b was a 163g. I will probably buy a 175g production run, just for a little bit more reliability in wind and for some added stability to possibly hold an anhyzer line.
-The r419b is extremely workable for a distance driver for me. I could see this becoming a workhorse driver out on the course (assuming the 175g adds that slight touch of extra stability I would want). But no matter what, the r419b will be in the bag for shaping all sorts of long distance turnover lines, sweeping hyzers, and tailwind bombs!