Despite being a Potter fan i have to admit that i did'nt enjoy this very much when it first appeared on television. But with a growing interest in science fiction over recent years i thought it was worth another look and i was'nt dissapionted. The combination of potter's drama and what sometimes looks like cheesy si-fi jarred a little at first but ultimately it all works.
Old Potter themes such as the impact of memory on the present (and in this case the future) are given a new twist and poignancy due to the writer's knowledge of his own death. It is rare indeed to find science fiction exploring themes such as religeon, the nature of reality, the impact of technology on society and so on with any kind of intelligence. It makes films such as 'The Matrix' look like kids stuff.
Yes, some of the characters seem a little over the top, and yes it may be that potter only used the genre out of neccesity to explore certain themes, but you will be hard pressed to find science fiction (or any tv drama) as challenging and absorbing as this.