IMHO the difference is like night and day.
Your LCD is brighter, more vivid, there are no signal issues (i.e. pixel clock fuzziness at times), etc.
I really didn't think that I would notice the difference until I tried a DVI card. Truthfully, until I put my LCD on a DVI connection I just liked my LCD, now I love it.
Go down to Fry's or Best Buy, get a DVI card, test the difference. If you agree, keep the card, if not return it. No worries...