9er fan here.
I've watched all of Purdy's snaps (probably multiple times). I am shocked at how well he has played. I am a Jimmy fan but the niners were avging 23/24 pts/game with Jimmy. With Purdy they are around 33/34 I think.
Here are some things I noticed:
1. He is surprisingly athletic/mobile. His elusiveness reminds me a little of Russel Wilson (pre-broncos). Probably not as elusive as RW but some hints. When he scrambles he is looking downfield. Best example was last game against the Seahawks he juked 3 or 4 defenders and threw a dart to Aiyuk in the corner of the endzone. Unfortunately Aiyuk dropped it but I was amazed of his craftiness. He is also very situationally aware for a rook. He scrambled once and slid (very smooth baseball slide) while reaching the ball towards first down indicator to get the first down and avoid getting hit. He does an amazing job scrambling to buy time, stopping, and setting his feet before he throws. He does have a tendency to spin to his left when facing pressure from his blind side. Last few games defenses have caught on to that and timed that spin better.
2. He is pretty accurate. This is true in the pocket, on the run and under pressure. He has a baseball background l so he throws from different arm angles to avoid balls getting batted down. He seems most proficient in hitting crossing routes in stride and allowing the receivers to get some YAC. He does a great job finding his check down and letting his check down receivers (CMC, Kittle, Juice and Mitchell) make plays. I did notice some nervousness in the first half of the last game. The first ball he overthrew a wide open Deebo by 5 yards (at least). Not sure if it was the rain or nerves. He also tried to dart some short slants that got batted down by middle linebackers playing zone and watching his eyes. We are lucky those were not intercepted.
3. He is not afraid to get hit. He will stand in the pocket, extend plays and throw while expecting a hit. This scares me a little because we have used all our 9 lives with injuries at this position. He has been a little loose with the ball when he scrambles. He hasn't fumbled but sometimes I see him scramble and I yell "protect the ball!"
4. He lacks arm talent. There have been a couple plays where he throws it deep. The receiver still catches it because he is so wide open but has to slow down. Good plays that could've been touch downs. Not sure if he under threw it or just didn't have the arm strength to get it there. The deepest ball I seen him complete though was against the Commanders (to Kittle). I think it was around 45 yards from point of throw to catch. A lot of crossing routes have been wide open because they sent a deep post route. I am curious to see if a team will challenge him to throw the deep route and have their safety sit on the crossing receiver.
5. He has poise, a lot of confidence (swagger) and good command of the offense. He gets in and out of the huddle. I dont remember any delay of games. He directs receivers when they are out of position. He has led 2 minute drives in almost every game he has played. Even saw him get on Aiyuk when he quit on a route.