Only render to the size you want for the final use. If you render smaller then you want, it will always look blocky, and pixellated. Cinepak is another OK format, that any machine can play back. If you want to use MEPG, get a better encoder then the stock one in Premiere. I output to uncompressed, then toss the file into Cleaner for my encoding, but it is a little pricey. The best use for MPEG is if your going to DVD. Then of course, you'd be using MPEG 2.