Im currently watching the third show, and this one appears to have more that will change (i dont quite remember from when i last saw it) But even being 20 minutes into it nothing has happened that will cause a noticable change (well except i know that Doc's death and also the picture of Doc with the clock tower will change) but even the changes that do occur are really fairly subtle.
besides, its just more of a food for thought type thing and thats why i didnt limit it to just back to the future but included type travel in the topic.
-Darth Simon