I did some tests (I always start the program and then immediatelly hit ctrl-D):
$ time ipython
$ time bin/isympy
$ time ./sage
I did that repeatedly, so this is the usual time I get on my laptop. I think ipython is quite slow, because:
In : %time import sympy
CPU times: user 0.08 s, sys: 0.01 s, total: 0.09 s
Wall time: 0.09
or if I import it in the python interpreter, it's immediate.
The 0.3s is acceptable, 0.5s is quite a lot for me, and 1.4s is a lot. I am maybe too demanding, but it just annoys me to wait for 1.4s on the import time. I just get some idea to try, so I fire up Sage or SymPy and try it. I don't want to wait for 1.4s.
This can be fixed, one just needs to find modules that slow things down, and late import them, or just fix them in some way. And usually, one does it several times -- I think Sage did that twice, SymPy also I think did that twice already.