from my point of view: no they're not similar.
except, at least partially, for the typical system related shortcuts mentioned by mnwij.
this is valid for the four free software four graphics i'm mainly using (scribus, gimp, inkscape, mypaint).
personally, i consider the two (three) programs to behave (and look) different enough that switching the context is easy enough... except for a few specific shortcut where it's a bit of a pain.
anyway, most of the time i don't use the same features (in the same way) in the different programs... and for some of the features i always use the keyboard in scribus, i tend to use the mouse in inkscape...
my hint? learn different programs for different goals, with different muscle memory...
(the most painful ones that come to mind: M, F1 and ESC to get into "move" mode... or the smaller movements for shapes (ctrl? shift? alt?).
(a convergence between the three programs would be very welcome... but it's not enough to have the same shortcuts, first they need to behave and feel the same!)