IME, and as i understand it, upscaling tends to be more relevant to the software of your upscaling devices and Tv combination.
If you have i good TV that upscales all it needs to on its own, for example, and you then add a good upscaling dvd player, you can, but not always, get a worse picture than with a non upscaling dvd player.
Upscaling can improve your picture. But depends on the particular software working on your particular screen. It simply fills in the missing info on a bigger screen with "something" that it thinks looks better. Weather it looks better or not to you watching it on YOUR tv, well thats a whole other story. What looks good on one set up can look shite on another.
No expert on the issue as i beleive i have a quality TV, upscaling not something i need or have gone out of my way to buy, and on two occasions made the picture worse when borrowed upscaling Dvd players from mates as an experiment also, a £350 Onkyo 1080p Amp which claimed to upscale made the picture consideraly worse.
Sky plus HD showed an improvement over sky plus, dont care how it does it. But from memory, Hd box was better when both boxs where scarted side by side. (not HD picture though obviously and had to un plug and plug in etc)
If dvd comes out same as 720p to look at, somethings not right with the tv or your 720p source/set up i would think.
Not sure re forceing a new epg download on a sky box. May loose your drive content. Not worth the bother or risk imho. Worth a google though as there are no issues when sky send it down to the dish obviously.