There is no way I could ever be disappointed in something Neil Gaiman is involved in. Saw the pilot a while back, and a month later I am still as excited as I was after that. Tom Ellis makes a fantastic mischievous devil, similar in a way to his Rush. This has the potential to become a great series, it sure has the characters for it. Also, I am a sucker for redemption stories, or any story that involves the devil in a capacity other than the boogie-man.
After the first episode I expect this series to be a roaring success. It has an absolutely stellar cast, the plot has me hooked and did I mention the absolutely fantastic actors? I would attribute the low overall rating to the fact that it could have been more fast paced, but as I see it more as a psychological thriller, personally I believe it is just the right speed for what it is trying to achieve. And the story itself is amazing, but no spoilers.
I am a computer scientist and I found the series refreshing in the way it viewed engineering. It is rarely the case that media portrays hacking in its unfabulous way that it is (yes, reverse engineering the IBM computer can count as hacking). So the story veers to the business side of the tech industry when it wants excitement and that's all right. The politics of it are fabulous.
Oh, did I mention the actors and how great they are. And Lee Pace? Especially Lee Pace. Very much LEE PACE!!!! (I guess you figured out why I actually picked up the series....)
[PS: I have only seen the first episode as work and university (exams) had to take precedence]