The lossless formats can definitely sound better than the lossy ones we've been listening to on DVD for so long now, but you should still expect there to be a good bit of variation from title to title (the quality of the original mix being at least as critical as ever).

Video performance depends on a number of factors, including screen size and viewing distance. The BDP-83 does such a good job of scaling that there will be cases where it can rival the HD disc if your screen size is small enough. (I ran into this with the hybrid HD-DVD of the last Bourne movie and my 983H, where the DVD side looked almost indistinguishable from the HD-DVD side when watching a 32" 1080i HDTV). There are some discs, though, where Blu-ray can really startle you with the picture quality - even on a modest screen size. I remember being taken aback at the picture quality and vibrant colors of Man on Fire when I first got Blu-ray.