[...] thats new to me, [...] about Shredder not being so important in the first comics.
He was important for the very existence of the Ninja Turtles, since Splinter trained them fifteen years as ninja to exact revenge. If you've seen the first movie, you pretty much know the origin story of the original comics, since it culls heavily from issues 1, 10, 11, and the Raphael and Leonardo one-shots.
But since Kevin Eastman and Peter Laird thought they'd only ever get an opportunity to make one issue of the TMNT, which they self-published (and continued to do for a long time), they killed off the Turtles' arch nemesis and that was it. From there, other stories developed—and later, the Foot were still an integral part of the stories, and
The Shredder made a return...sort of...and it's a pretty ghastly tale (covered in the totally badass Return to New York arc, which were issues 19–21).
I'm actually pleased with the direction the 2003 TV series took in making The Shredder a rebellious and very powerful Utrom. Considering Laird wanted the cartoon to be as close to the original comics as possible, it was a good solution in order to still have The Shredder around in a big way.
Anyway, I'm not hopeful for the upcoming movie, but I am excited for the Nickelodeon cartoon, and the current comic series by IDW is pretty neat. (Haven't followed it in a few months since I decided to just get the trade paperbacks. Cheaper and easier to store/shelve.)