As with all the Red Giant Software releases, there's a trial available. I'd suggest you try it to see if it meets your needs.
I think that Instant HD is pretty good, but no upres software is magic. Any time you resize from SD to HD, you must balance between softness and processing artifacts, and the quality of your source footage will have a big impact on the quality of your upres.
If you have a video I/O card (like an AJA Kona), you may have hardware resizing options available to you.
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