Allocatable variables slow the code?

I read the discussion in the topic 'Allocatable array' (issued 2008)
I didn't understand the answer. Allocatable variables slow the code or not?
I understood this problem could be found in debug mode, but the performance should be similar in release mode. Is this?
My Os is Win7 with Intel Fortran 10.
Allocatable is useful, but I don't want to sacrifice computational efficiency.
Since I am starting my project, I should understand this point now.
Regards