I am using Z3 Python bindings to create an And expression via z3.And(exprs) where exprs is a python list of 48000 equality constraints over boolean variables.  This operation takes 2 seconds on a MBP with 2.6GHz processor.
What could I be doing wrong?  Is this an issue with z3 Python bindings?  Any ideas on how to optimize such constructions?
Incidentally, in my experiments, the constructions of such expressions is taking more time than solving the resulting formulae :)
Using Z3 over Python is generally pretty slow. It includes parameter checks and marshaling (_coerce_expr among others). 
For scalability you will be better of using one of the other bindings or bypass the Python runtime where possible.
Why is z3.And() slow?