I think the Expo will do more good for Shanghai than the Olympics will do for Beijing. Just the other day I got yelled at by my co-worker for saying that the Expo isn't as big a deal as the Olympics. I stand by my point, but, I believe that while the Expo won't be so publisized and closely watched as the Olympics, it will do Shanghai a lot of good.
For the Olympics all Beijing did was build a few subway lines (line 5, 10 and 8) and some hotels and some nice venues. They really didn't make the city as a whole look nicer. They may have fluffed some areas up, but I remember the sidewalks by my house were still all broken when the Olympics was happening.
I think that since the Expo is kind of to show off the city, and that the venues are all funded by the governments of the respective countries, Shanghai is really trying to make the city look nice. They are also building a massive amount of subway lines ( line 7,9,10,11,13 and line 2,8,6 extentions ) They are burying a ton of power lines, painting all the ugly buildings, replacing every sidewalk with even as much as one crack, re-paving roads, building 3 new road tunnels and a new bridge. etc. These improvements will not only make Shanghai look nice during the Expo, but it will also make Shanghai much more liveable and nice in the future. I love the expo, I even bought a Haibao doll