I've taken this bloom a number of times using different cameras and lenses. I believe I posted an image here of the very same flower taken with the Fujifilm X100S. The colours from this combination as well as contrast are stronger than from the X100S but if I don't prefer one or the other. I like both, the X100S colours being more pastel. I would say it depends on the function for the image, where I would use it and in what context.
However, I think the image above turned out quite ok; nice and sharp and the bokeh is also good. The Pentax 135 f3.5 is quite small and fits nicely on the E-PL1 but don't forget all these old long prime lenses are all metal so the combination is a little front heavy.
