Some of the more prestigious film festivals will only screen your film if it is on actual film or if it's in High Def.

I'm facing this possibility myself and am wondering if we could devote a thread to this. Not only do-it-yourself methods but also what the best way to uprezz is if money is not an issue.

I get quite good results just from using After Effects and Magic Bullet Deartifacting plus a selective sharpening method.

No-Sharpening:
http://www.bargus.org/720p.jpg

Regular Unsharp Mask:
http://www.bargus.org/720ps.jpg

Selectively Sharpened:
http://www.bargus.org/720pss.jpg

I didn't get any better result going up to 720p for processing then back down than just sharpening at SD res (and it was far quicker):

No-Sharpening:
http://www.bargus.org/576p.jpg

Selectively Sharpened:
http://www.bargus.org/576pss.jpg

Quick question: I have Magic Bullet (at least in PPro) why isn't the deartifacting showing up in my After Effects?

You mean the plugin? If you've got it working in Premiere I'm assuming you've got the editors edition, I don't think that version supports After Effects. You need the suite.