OK, so I know as a Torchwood fan how mixed the reviews are, but in light of it's iminent return I thought I'd add my opinions.
Torchwood was meant to be the more adult version of Doctor Who. It has achieved this, in Sci-Fi terms at least. There's sex, guns and violence. There's homosexuality, there's adultery, there's plenty of snogging, basically. Torchwood employee's seem to be obligated to snog their boss/colleauges a lot.
But once you get past a few dodgy episodes (Sex gas, anyone?) Torchwood comes into it's own. The first DVD, this one, is a good introduction, but I would urge anyone who watches it not to judge it just on what you see here. As the series goes on, the episodes get steadily better.
The first series of Torchwood was entertaining, but also a learning experience for the writers and producers. We've learnt things such as we now realise Chris Chibnall should never be allowed to write episodes.
I'd reccomend Torchwood less to hardcore Sci-Fi fans, who will probably be very dissapointed, but more to people who are fans of Doctor Who, but would like to experience something less aimed at children.
I can only see Torchwood improving in it's second series, and as long as Chris Chibnall is allowed as little control as possible, it should be great!