I find the 2D math input in Maple to somewhat cumbersome for various expressions.
Specifically, I have a function f(z) = z^2, with w = f(I x + y) where I is the imaginary number.

I typed the line in 2D math

plots[implicitplot]({Im(w) = 2, Re(w) = 2}, x = -5 .. 5, y = -5 .. 5, colour = {"Blue", "Red"})
Error, (in plot/color) invalid color specification: {"Blue", "Red"}

For some reason this does not work in 2D math, but in Maple-input it works as expected.

I recall from past use of Maple, that there were other problems as well with the 2D math input.
I know you need to be particular with the use of space. 

Are there other common pitfalls or "bugs" related to use of 2D math input ?

I try to define an ellipse using the geometry package

with(geometry):

ellipse(e1,['foci'=[[0,1],[4,1]], 'MajorAxis' = 8],[x,y]);

I get the message:  Error, (in geometry:-ellipse) wrong type of arguments

but the documentation tells me that I can define an ellipse this way...