I was in the pro-Fellaini camp last year when we signed him. Obviously he has a poor season (who didnt?) but look at the circumstances;
1) last minute signing. Season had already begun and if memory serves he was carrying an injury. Remember Berbatov? He also struggled to fit straight in having been bought in similar circumstances. He has had a limited preseason due to the World Cup, but enough to make a difference.
2) rumour was that Fellaini was carrying an injury for a fair bit of last season (wrist, I think?)
3) again, the entire team had a collective 'mare last season
Fellaini may still be sold and he still has a lot to prove, but those writing him off after last season are likely the same people writing the entire squad off before the season has even begun.
He showed what he is capable of against Valencia. Only 20 odd minutes but he was our best player and changed the game when he came on (and won it for us). Playing in a new system, with a good player like Herrera next to him, I reckon he could well come good this year.
If you think the above is so outlandish I invite you to consider Ashley Young - most of us (myself included) wanted him straight out the door this summer. LVG found a role for him in the new system however, and he has looked like a different player.