Simon .... do you have AIS as well as radar ? (Hi to you both btw, trust all is well with you.)
LoboPops .... maybe a house roof will be visible to the naked eye but the reality is that even awake it is going to be pretty damn easy to miss the odd log or tree trunk. On passage, how many solo sailors are keeping a full time forward lookout ? Very few methinks. I rarely sail solo these days but on anything over ten hours or so for at least part of the time there will only be one of us on deck and that one is probably sitting in the cockpit looking aft or abeam.
For mine I like AIS. Picks up pretty much all commercial craft these days. A while back we were caught in a pea souper off Sydney with a tanker moving up the coast and into Sydney Harbour. Without AIS I would have been ever so slightly on edge.