The latest episode of Doctor Who (Saturday 21st June) demonstrated both the strengths and weaknesses of Russell T Davies as a writer of SF. I seem to recall reading an interview somewhere in which he acknowledged that original ideas were not his forte and it is true that he seem to cheerfully pillage ideas from everywhere. The range of references and plot ideas he drops into an average episode is huge. This works well with his great strength I think - he is simply brilliant at world building. The last episode - and the two part season finale to come - seem as if they will depend on a series of small visual and narrative clues built in to previous episodes going back in some cases over previous series and even to the old Who from years back. At the time some of this at the time seemed merely to be 'fleshing out' the story line, but in many cases they turn out to have a significance out of all proportion to their impact on the story line at the time. His juggling of these ideas as both writer and executive producer is a world apart (sorry!) from the dross of Heroes or Buffy. I suspect if Firefly had been able to keep going it might have achieved something similar. Other than that only Babylon 5 seems to have taken the world in which it was set seriously enough to make it coherent, and within the story line, believable. Let's hope Stephen Moffat proves as good.