I was really looking forward to watching this movie and I have to say, was a little let down. One of the most annoying things is that there is no mention or relation to the original characters, so we have no idea what happened to them.
The new characters, actors and direction was pretty good, I felt put into the situation. The down side is that the way the infection starts again is just, strange. It kind of makes sense but the way that the infection spreads just silly.
The other positive is that this movie clearly had a bigger budget. Lots more shots of London deserted as well as cool action shots across the capital, painting a much clearer picture of what it would be like.
These positives are, unfortunately, all dealt out early on. What you're left with is many frustrating events and character decisions, held together with disorienting and unrealistic scene movement.
In conclusion it's a good start, with a weak middle and unbelievable execution. Ending is wide open for a third though.