# How about after normalization?
qplot(getRatings(normalize(MovieLense, method = "Z-score")),
      main = "Histogram of normalized ratings", xlab = "Rating") 
summary(getRatings(normalize(MovieLense, method = "Z-score"))) # seems better
# Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
# -4.8520 -0.6466  0.1084  0.0000  0.7506  4.1280