OK, BluRay is better, but I don't see a big enough difference to change from DVD's, especially since I see BluRay as the 8-track of this decade. It's a stop gap.
Have you seen Blade Runner in BD compared to DVD? I mean it is like night and day. Same for Harry Potter. Same for Pirates of the Caribbean. I agree there is the odd movie where there is no improvement and I would not suggest to replace an entire DVD collection but it makes sense to be buying BD rather than DVD these days, IMHO