I already own 4 copies - 3 on VHS and 1 on DVD. Here's my current inventory:
Original Trilogy on VHS. This is a full-screen version. Back then, we didn't consider the widescreen version.
Digitally Remastered Trilogy on VHS. Still full-screen.
Special Edition Trilogy on VHS. This is the version that Lucas changed.
Trilogy on DVD. I have to admit, the viewing experience is much better on DVD, with widescreen and better resolution.
Than being said, it might be worth the upgrade.