It really depends on what you consider a good shot.
If you want the castle in the background, then try for a FP (currently in town square with a portion looking straight down mainstreet)
I don't usually watch from Main Street because it is crowded and you never know who will be near you. Sometimes I have the perfect spot, only to have a family sit in front of me who likes to lean into my shot. Or I'll stand behind the sitters on the curb and then suddenly everyone will stand for no reason. With how straight the road is, any one person can throw off the whole shot and you aren't left with any room to adjust your angle.
I love Frontierland and getting shots of the floats at step-off. The path is much wider in Frontierland, and it's easier to focus on the performers without worrying about too much noise from the other guests. Or if you can get the right angle, having Splash in the background can make for some cool shots. They also move more slowly in the beginning of the route while everyone comes out, so you can get a few more seconds for photos with each float. Because of the angle of the route (it's not a perfectly straight road and is a bit of a hill), you can also get some cool shots of the back of the floats looking down the length of the parade.
Liberty Square in front of Hall of Presidents can give some nice shots as well. You can get the floats coming around the corner, going straight in front of you, and going across the bridge. You also get the performers in full performance mode here. The dances will be modified a bit in the beginning/end while the floats are coming out/going in, but in the middle of the parade they have the tempo down.