We recently spent a week in London and used the buses to great advantage with our one-week Travelcards. Our apartment was on the south bank near the Tower Bridge, and while we love to walk everywhere, we preferred to us the bus to get to Nd from evening activities like plays or opera, and at the end of a London day of walking to get home. You get nice views of London from the upper level, and on the #11 going to Chelsea for dinner we got a personal narration by a local along Kings Road. The #15 was great for getting us back to Tower Bridge from the Aldwych/Strand stop near Covent Garden, and one evening we were treated to a bridge opening as we crossed.
We bought a good bus map for £2.50 and combined that with an app on my husband's phone to figure it all out. Very easy and pleasant.
I don't like riding the Tube because of claustrophobia, so the bus is a great option for us.