I think it will be mean more people flying low over residential areas resulting in more noise complaints. I also think there will be a greater risk of someone getting themselves in a position from which they do not, in fact, glide clear.
I read a report by the CAA saying that they did not intend to change the 500ft rule as they, quite rightly, felt that the UK wording was far superior to the ICAO wording. What prompted them to change the 1500ft rule then?
This new rule is an Aerial Photographers' Charter and is not good news for the image of GA.