Being a Cal fan here in NorCal, I can honestly say that Goff kind of scares me. He is wildly streaky. Can look all world one minute, then like a confused mess the next. Now one thing that has always had me give him the shadow of the doubt is the fact that since he has been the starter at Cal, they have not had nearly the quality of RB that Cal is usually known for. His OL has also been up and down ... and the WR's are up and down as well.
He is a pretty cool cat in his demeanor though if you watch him on the sidelines after something bad happens. He usually looks like he has shook it of ...but he doesn't always seem to show it on the field of play.
another thing ... he was VERY slight of build coming out of H.S. at Marin Catholic. He is just now starting to get his body to where it should have been two yrs ago. He may still take some time to get ready for the NFL pounding. But like Aaron Rodgers (who I have known since his HS days) is very good in mechanics. footwork, reading progressions and for the most part pocket awareness is pretty decent.
But all that said .... he leaves enough "wince" in my opinion of him to say I would NOT trade up for him. I truly don't think he is as NFL ready as Rodgers was coming out. And he is not quite as "mobile" as AR either .. .so that "still developing body" may slow his readiness to start right away.
Drafting a QB is a crap shoot. There are NEVER any "sure fire" prospects. I would put Goff at the 50/50 category of whether or not he will ever live up to his pre-draft "hype". But if they pulled the trigger if he is still there @15, I could be good with it. I just wouldn't use capital to move up.