I'm most of the way through Invasion and I would recommend it. The plotting and story unravelling is reminiscent of Lost, though moves more quickly. There's Lost-like character conflict, secrecy and hidden agendas. Two families form the central cast in a Spielbergian split-family style with bursts of teenager v parent angst. It's an intriguing update of the Invasion of the Body Snatchers concept, and feels like it could have been inspired by more than a few X Files episodes.
It definitely has some flaws: I found it impossible to believe that the teenage boy was supposed to be the child of one of the split couples (this seems to be common to lots of TV dramas though); too many story threads and events dissipate with too little explanation. However, overall, it's well worth watching: it's nicely shot and edited, and some of the principal actors are very good - the small girl, for example, does a great job.