I just tried to benchmark a suite of plots in 1.1.1 and then in 1.2.0 (Windows 64). It includes line plots, scatters, bars, contours and surfaces.
(The underlying notebook is at https://github.com/PaulSoderlind/JuliaTutorial/blob/master/Tutorial_04_Plots.ipynb, but you can easily download it as a .jl file to run it in the REPL).
Julia 1.1.1: 70 seconds
Julia 1.2.0: 150 seconds
(on a half-decent notebook).
I have now updated that notebook to use a slightly different
plot() syntax that seems to avoid the 1.2.0 performance penalty. Basically, avoiding