Most anime today and over the last few years has been animated natively in HD. The only exceptions are those which are animated by J.C. Staff or Bones who animate at 540p, not to say that their shows don't look much better on BD. Soul Eater for example is an upscale, but actually looks pretty good. The difference to me is like night and day.
DVD's are interlaced, heavily compressed, have washed out colour and PAL DVDs also suffer from PAL speedup.
Blurays are progressive, have over 4x the bitrate the play around with (40+ mbps instead of 10), don't have washed out colour, and play at their native speed.
Usually I would go on a rant and supply images but I'm not feeling up to it at the mo', so I'll say YES YES YES, there is a massive difference in quality between anime on DVD and Bluray, and you'd be crazy not to notice it - especially as shows are looking better and better.