Hi Rafael,
I did some unscientific tests with Instant HD when it first came out and my results had little artifacts throughout, like pixels or groups of pixels that would sort of crawl, wiggle around and sometimes just sort of flip out like the signal was breaking down there. I found the upres results with Compressor (since version 2) to be much better, as long as you use its highest quality settings for scaling.
However, I was testing with relatively low quality SD footage, uprezzing to HD so that really pushes the capabilities of the software. You can of course download the Instant HD demo and try it yourself, it may be better if your 720p footage is already pretty sharp, etc.
You can also try
Digital Anarchy Resizer, but I believe this will also not be appreciably better than what you've got with Compressor. The retiming/resizing algorithms Apple built in there since v2 are really very good
Best of luck
LMN
Lu Nelson
Berlin, Germany
