I would always watch Monfils, he is entertaining most of the time, even in practice, he is also available and friendly to fans. I think he was very nervous coming in yesterday, knowing it is Nole and that it is a major semi final. I think he just started badly and really wanted to change something. Perhaps he had Simon's match against Nole in Australia in mind, he almost pulled it off then drawing 100 errors from Nole.
As for the roof, I know it is an outdoor tournament, AO is also and they do have the heat policy but not until the temperatures reach 104 F and perhaps not until the temperatures are 122 F, the deciding factor is the humidity level, but when it is 100 degrees on court with humidity, who can really expect players to play their best. They are not robots. For those extreme cases I think it should be utilized for everybody's sake, when the roof is there anyway. That's just my opinion, not that it matters to anybody, really.