The roads are a lot better than the original, dark tarmac with sharp yellow points, they look fantastic. You can also play with it anyway, the stunts which are performed on roads like main streets and beach side roads, or the roads by the skyscrapers, should be the dark HD ones. Roads around the slum areas can just be the original ones (which is why I have two versions, one with the new roads, one with original).
Can't say anything about the palms yet as i'll need the combined generic.txd, but from the images they look 10 x better than the original, more vibrant, more accustom to the 'miami look'.
Not starting an argument here, just stating my reason for preferring neo's roads in the correct areas.