Revelations probably worked least well for me, being the culmination of a couple of long-established Battlestar Galactica story arcs. The revelation that a key character was actually a Cylon makes little impact if you don't know what a Cylon is. The quest for Earth wasn't explained here, so the importance of finding it again was a bit puzzling. But the acting was generally good, the hostage-taking situation engaging, the production values excellent and the music at the end haunting. I will probably put it fifth on my ballot but that doesn't mean I didn't like it.
By contrast, The Constant pulled me in from the word go. The basic concept is of someone adrift along their own time line - see Slaughterhouse-Five, The Time-Traveller's Wife and "If This is Winnetka, You Must Be Judy". I must say I would never have thought it could be pulled off in a visual medium, but they have done it very well, with Cusick and Davies as Desmond and Faraday turing in superb performances. There is an obvious nod also to Flowers for Algernon. Slight loss of marks for referring to the non-existent physics department of an Oxford college, and for a little too much acting with your beard at one or two points. But I think I will rank this second or third, competing with Turn Left, which had a similar theme but done less satisfactorily (but it is Doctor Who).
Dr Horrible's Singalong Blog is an entertaining enough one-off Joss Whedon production, reminiscent of Once More With Feeling but to be honest not really as good. Neil Patrick Harris/Dr Horrible's monologues to camera, and Nathan Fillion's testosterone-fuelled Captain Hammer, are the most interesting things about it, but one feels that one is being invited to admire the production not because it is being done well, but because it is being done at all. Still, it did make me laugh out loud once or twice, which I rather regretted as I was then immediately reminded of why I was lying in bed watching.
So, in the end, my Hugo ballot in this category will probably be:
1) Silence in the Library/Forest of the Dead (Doctor Who)
2) Turn Left (Doctor Who)
3) The Constant (Lost)
4) Dr Horrible's Singalong Blog
5) Revelations (Battlestar Galactica)
Though I am still musing the second and third placings, and may swap them.