Power of the Dalek Reflection
As with any life-threatening event, the process of regeneration is shown to have a traumatic effect on the first-time regenerated Timelord. During regeneration, the Doctor's hearts are heard to resonate rapidly at first then slowly stabilize. After the Doctor recuperates he states, "it's over". I believe, however, that the Doctor was a bit premature in making that statement. Although his bodily structure had stabilized, the Doctor's mind still had miles to go to fully acclimate to his new body.
The first evidence in this acclimation process was when the 2nd Doctor saw the face of the 1st Doctor in the mirror, then the image was quickly replaced by the reality of his new face. The conversation with his confused companions led the Doctor to make other statements which questions his state of mind. First, the Doctor speaks of himself in the third person by saying, "the Doctor was a great collector wasn't he?" Polly immediately identifies him as the Doctor, but the Doctor refutes the claim simply on the basis of physical appearances. An even more confused Ben, doubting his own identity asks the Doctor, "who are we?" The Doctor replies, "don't you know?" Responding Ben's question with a question denotes that the Doctor, on some level, was unsure of who he was. Because he had just gone through the most traumatic event for the first-time in his already long life, the Doctor was in doubt of his own identity and with good reason.
The conversation moves forward and the Doctor concludes that he has been renewed and soon makes the connection that it is a process, in tandem with the TARDIS, without which he could not survive. I would say that this was the 2nd Doctor's first significant milestone. He realizes that he "thinks therefore 'he' is" and all that is left now is to 'shop' for a new personality.
Of course, at first he still sounds like the 1st Doctor when he says, "come here!" to one of his companions in the same tone and air of superiority as the 1st Doctor. Then soon mellows out and requests to see the "Doctor's" dairy. As far as I am aware, the 1st Doctor had no real interest in music; yet, the 2nd Doctor begins to explore his new psychi for interests and finds out that he enjoys playing the flute. An interest that the Doctor picks up again in his 10th incarnation--remember Music of the Spheres? The 10th Doctor is a music composer.
The Power of the Daleks is a rare kind of story due to the fact that not often do you find Daleks as servants to lowly humans. Of course, the Daleks were only pretending to serve humanity in order to follow through with their plans of conquest. It is noteworthy that the people of Vulcan had heard next to nothing about the Daleks. From scientist Lesterson's initial attitude towards the Daleks, which was one of curiosity and elation, it would appear that the galactic community had not yet suffered the full brunt of Dalek attacks and plans of extermination. Another fact that contributes to the rarity of the story is that not many other stories; except for Genesis of the Daleks, will have presented Daleks starting from 'infancy', so-to-speak, and in a mode of reproduction. Most Dalek orientated stories will have shown, from the get-go, the results of Dalek achievement and supremacy already in place, but never in such a delicate beginning. Indeed, it is interesting how the Dalek mantra shifts from "I am your servant" to "exterminate".
There's a lot more to say on the matter, but I'll conclude by saying that I give Power of the Daleks 5 TARDIS groans out of 5, because this was our first regeneration story. And not only that! The first regeneration story taught us that the Doctor suffers a bodily death, then recovers to find himself in an existential crisis only to be followed by a profound identity crisis. This pattern sets in motion a chain of events for later regenerations to follow--a pattern that forcibly gives the show a quality of character 'sine qua non'--like no other. With the soon regeneration of the 10th Doctor into the 11th I say, "Shop on Doctor, for another brilliant and electrifying new personality".