There will be a second & third series of twelve episodes, six adventures, each. Probably.
Sarah Jane – The Return. UPDATED!The rest of the episodes of the first season on SciFi will be half-hours, but they'll be transmitted back to back, so it'll be a little bit old Who (half hour eps with cliff hangers) and a little bit new Who (hour long adventures).
This first episode was also the pilot, so there are some tweaks introduced in the next, regularly produced, episode. Don't think there's any kind of season arc, though I imagine the Bane will pop up again sooner or later, if not this season then series two. I think an old UNIT friend is supposed to show up sometime this season.
All in all a solid start. I think it played better than the first ep of Torchwood, if that's not a apples and oranges comparison.