I'm glad Bert 'got it' (we should all get it at least once in a while)
I watched it again last night and still didn't like the end.
Why did the Dalek's programming not correct the error? Why did we not have a few minutes of it thinking 'oh god what's happened, i am a bad bad sentient being' before it's core programming took over and ousted the nasty Billie-gene (thus giving Rose enough time to escape).
That would have been cool. The Doc could still have gone nuts, we could have still all got in touch with our inner Dalek, but the thing would have reverted to type - as it should be - and we could have had a much-loved 'yeah they're back' explosive ending, rather than a wimpy - if rather good on the SFX - suicide.
BTW, Outpost Gallifrey has a whole link for people who hated the ending and are having to go into therapy to be assured the Daleks will be nasty again next time - so it's not just me and Lord S. Nyer!!
Zebras deserve everything they get.