I'll kick start things by giving my perspective. I'm firmly on the side of patience. I don't think he's been great at all, I think he slows down play, is way too scared to bring the ball forward, opts for the easy pass, and sticks out like a sore thumb in the midfield. However, I'm willing to give him the benefit of the doubt for two reasons.
First, it's hard to settle here. I've made this argument before, but it's true. Henry, Suarez, Villa, Alexis, Alba, Sergi Roberto, Mascherano, Fabregas, and Neymar have all been players who have had good to great spells here, and all of them took half a season to a full season, or more in the case of Alexis and Sergi, to reach their highest level. Most of these players were also much more experienced than Gomes was when he was signed. If these players came good with a little bit of patience, so can Gomes.
Second, these problems are not unique to Gomes. Rakitic is having his worst season so far. Busquets, who used to epitomize consistency and reliability, is having the worst season I have ever seen out of him. Everyone wants to see Denis but after his promising start to the season he's slowed down. Rafinha has been good but hasn't quite gotten back to where he was prior to his injury. Iniesta has been absolutely brilliant at times, like his appearance in the Clasico, but is also clearly showing his age and is increasingly inconsistent. If everyone else in the midfield was brilliant and Gomes was terrible I'd be concerned, but this is a near universal problem for Barcelona midfielders this season. Nobody is playing to their level. Gomes has been singled out for his price tag and consistent play time but how can we blame him, when he's in a new team famously difficult to adapt to and nobody around him in midfield is playing well either? Chances are his confidence is in the dump, which would explain a lot why he isn't decisive and opts for the safe lateral and backwards pass. Confidence is a footballer's wonder drug, and maybe when he gets some he'll show something he hasn't shown yet.
Patience is a virtue. We didn't spend that money without doing our research, let's give him a little bit and stop blaming him for whenever we play poorly. We didn't play any better against Depor when he came off.