I liked Legacy. The plot wasn't always there, but I didn't care. I loved the 80's and seeing the old graphics from the original recreated in Legacy with the brilliant set design and mind blowing sound track created an imaginative world that came alive. The Cycle battle is thrilling. And that Daft Punk score! The only thing that rubbed me the wrong way, besides the ho-hum passable story, was cgi Jeff Bridges. He looked... weird. They should have got the artists that did the recent fast and furious face cgi work on that.
But on a semi-related note, what needs a sequel MUCH more than Tron Legacy is Tron: Uprising! Oh my god! That has to be one of the top ten animated shows I've ever seen, sporting quality writing and story telling the Tron Movies could only dream of. Gut wrenching that Disney dropped the axe on a cliff hanger like they did, but perhaps not unexpected given the more grown up themes on display in the cartoon.