The positives insofar as signing Johnson is concerned seem, to me, to be limited to what an American politician might perhaps call 'non-negatives'.
Although he has played a lot, the team hasn't become totally derailed by accommodating him (does happen, see Asprila at Newcastle). Also, we haven't collapsed into serious relegation trouble. Again, can happen. A broken spoke in any wheel can cause the bike to wobble!
Basically, his arrival hasn't cost us anything apart from money. Lots of money. Loads by our standards. Still, some signings sink the ship and that's not the case here. Even if he never comes good, he hasn't ruined us!
In terms of reasons to be cheerful, there is no obvious reason to think the boy has a poor attitude. If anything, I'd like him to be a bit more of a kent, as good forwards can sometimes be a bit bolshy. Anyway, it's not like there's any reason to think he's not bothered. That shouldn't be noteworthy, but it's not something to take for granted with expensive footballers.
On top of that, he's scored goals before. It's not like he can't do it.
We play a very particular system, which doesn't seem the same as the ones he's played in before. He might be struggling with that.
He's still young. Whatever he wants for himself, it's in his interests to do well at palace. And ours. He isn't a Benteke or Sakho in that respect, he's not playing in the knowledge of a very narrow and limited future. If he comes good he's got time to go back up to the very top, and we could make money on him.
That said, Christ on a f***ing bike he's been absolute s***. As things stand he's surely in the conversation for worst signing in our history. Benteke would at least sometimes score.