I've two issues with tonight's first episode:
1. River Song – The Doctor did not know her at first, but (despite all the timeline complications) we know he met her in the guise of the Tenth Doctor (David Tennant) http://en.wikipedia.org/wiki/River_Song_(Doctor_Who) in the Library before she died. So we know that he knew her already. Mistake? Or some complexity in the timelines that is to be explained?
2. If (and Stephen Moffat was very clear about this in Doctor Who Confidential) the Doctor we saw die, really is dead; then producers have handed his agent a big fat weapon. If there can be no more actors in the role after Matt Smith, then when he goes, the series goes.
Personally, for some years I have thought that the production team would find a means to a \”super-regeneration\” that would reset the regeneration count back to 0 so that the series could continue indefinitely.
Or maybe Moffat and co have some trick up their sleeve so that he's not really dead; or it was a Doctor from another reality (remember Tennant is still stuck with Rose in an alternate reality already)