I guess it does depend on the area. But yes they do tend to leave items at other. The other week I had a parcle from the US and they didn't even knock on my door and gave it to the old lady across from me. It was meant to be signed by me, as it was a very expensive parcle.
About a year ago I had some desinger kitchen wear and as it was a smaller order the lady decided to deliever it 2 weeks later on a sunday using her own car rather than the one she was meant to... wasn't very happy with that.
They also once lost a gaint rat cage, which turned up 3 months later. Personally I'm sure they are ok for some thing, but I've had too many problems with them.
Complaining doesn't seem to get any where really, so now when I'm given the choice between them and another company I pick the other.
I might just be unlucky though.