I enjoyed this, it had a different tone to a lot of the new sitcoms of late. I think they were paying homage when they had Duncan doing a Dr Evil impression and the main guy doing an impression of Harry Enfield's teenage character Kevin.
My only surprise is that its not a sitcom that can have much longevity at all. Once the impending wedding arrives its over. Even if its cancelled he won't be Plus One anymore.
Unlike Gavin & Stacey, Worst Week of my Life, Nighty Night they haven't given themselves any credible window for further series.