Every time I saw Star Wars that year (eight times in the first six months of release) the crowd also burst into applause when the Millenium Falcon went into hyper drive.
Same here. My earliest memories of film going include the audience enthusiastically bursting into applause (for the nannies being blown away in Mary Poppins). Audiences have always done this, hopefully there will always be movies good enough that they continue to applaud.