Back when I had a non-fixed pixel HD display, I used a DVDO iScan to line double the output from my LD player - because the display did not have 3:2 capabilities (even though it did do line doubling) and the DVDO did. The DVDO worked as advertised.
As for their current generation of units: I've not seen any in action but I have read a few reviews. Apparently they also perform mostly as advertised - but that any improvement when upconverting say a DVD's output is minimal. Given their price, and assuming you're looking for improvements to DVDs, I'd say you should find a DVD player that upconverts to 1080i and outputs that signal via its component cables.
The DVDO concept was great in its day - but it's living on borrowed time.
With fixed-pixel displays and BlueRay and HD-DVD, I personally think that buying the VP30 would be a huge waste of money.
Keep your current display if you'd like. Buy a new playback unit (or HD cable / satellite box if those are your primary sources) instead. You'll be much further ahead.
Jeff Mackwood
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Jeff Mackwood