At first I was upset that David Tennant wasn't going to be The Doctor anymore, but that's the life of the doctor, ever changing. I'm not worried about This new guy (Matt Smith), what I am worried about is this new season being "Glamorous". The fun thing about the series is the women he chose as companions were fairly ordinary and of all ages. I think that by choosing a younger Doctor and younger or younger looking companion they might be reaching too hard to try to connect with a "younger/new" audience.
As long as it doesn't disrupt the story lines I don't mind.... but another fun thing about the previous Doctor Who Episodes is that the tension of attraction and love between the characters was part of what made it to fantastic. If they instantly fall in love with one another and he forgets all about Rose Tyler I'mna be pissed. This new girl looks like a ditz. I hope to be proven wrong. ... but honestly I really liked Donna. You could tell the two of them were on an adventure and that they were just partners. That was really nice.
Rose Tyler will always be #1...