I think for some people, he just has a credibility problem. I don't think he will be forgotten as the 'one after Tennant' - he's got Moffat as show-runner, and a largely clean-slate to begin with in terms of story-strands.
There's this 'darker' thing coming through from the promo-shots, and some of the comments I've seen, but I'm not sure it's more than wishful thinking because he's got the 'twilight' thing going on.
Besides, we had 'darker' with Chris E. battle-scarred and traumatized, and I'm not 100% convinced that Moffat wants to do darker, really, despite his scary reputation, he's quite a fluffy-bunny in terms of body count. He gave us 'Everybody Lives!' after all.
Do you know, it's nearly 24 hours, and I'm actually properly getting interested in how it's going to work. Curse my fickle ways! Not simpering though. Raising one curious eyebrow and folding arms.