I am liking series 6 more than 5 or 4 so far. If there is a difference from older Peep Shows it is probably because everyone (stars, characters, writers, viewers) is more familiar with each other and we are all a little bit older. For that reason I think it will be hard to beat the first three series but this one is very good so far - no coincidence I think that it has focused pretty sharply on the central relationships.
BTW I'm not a fan of the dog episode either (not on grounds of taste - I just think it made the characters do things I couldn't swallow).