Poor David Gooderson never stood a chance. Michael Wisher, whose dynamic performance created the character of Davros in Genesis of the Daleks, was unavailable to reprise his role as the Daleks' creator in this story, so the production team was left with no other option but recast the role. Gooderson was chosen to play Davros, and he gives a fine performance on it's own. However, Wisher's performance casts a long shadow, and one can't help but think of Wisher's Davros when watching Gooderson. To further hamper Gooderson, he's forced to wear the ill-fitting mask originally created for Wisher in Genesis.
It's the fact that Davros has even returned in this story that signals the end of competent Daleks for the foreseeable future. No longer capable of functioning on their own, the Daleks' sole mission in this story is to find their creator to help give them an edge in their role with a race of robots, the Movellans. It's even heavily implied that the Daleks are now robots themselves. When did this happen? Plot developments in the post-Genesis era have all been retrofitted (by fans, mostly) to tie in with what The Doctor did to change history on behalf of the Time Lords in Genesis of the Daleks. Convenient, that, but at the time, this jarred alarmingly. Robotic Daleks are the exact opposite of what the original Daleks stand for - pure hate. Robots don't hate. They're cold and logical. Daleks have never been logical, which is what made them so frightening. Logical Daleks are never frightening because we know exactly what they're going to do.
What I didn't expect to see, though, was a remarkably cold and callous streak from The Doctor. Whilst holding Davros hostage, the Daleks bring in some prisoners to exterminate until The Doctor gives himself up. Surely The Doctor knows the Daleks well enough that they're not going to bluff, but he plays along with them and watches the Daleks shoot down two prisoners and are an instant away from gunning down prisoner number three before The Doctor finally asks them to stop. So two was acceptable, but three was the line? You could almost hear The Doctor yelling, "This has gone on just long enough!" (you know, after he told the Daleks to "spack off").
Later, The Doctor continues his bloodlust by actually detonating a grenade that was affixed to Davros's chair before two Daleks managed to pry it off. What's more shocking is how casually he detonates the remote control when he's operating his sonic screwdriver. And then when he hurls a Kaled mutant against a rock late in the episode, he adds cruelty to defenceless species to his list of crimes in this episode.