Originally Posted by Indora

This is not true. Autoshot casttime is affected by haste.
It's very easy to test!

As we all know, Quartz can show the delay between the client & the server.
What Quartz does, is to count the seconds that elapse from the moment you click the steady shot button until the moment the cast starts.

Now all you have to do is to start an steadyshot with the following macro (we all know this one):
/cast !Auto Shot
/cast Steady Shot

You'll shoot an Auto Shot, instantly followed by the steady cast.
Because of the way the Auto Shot mechanics were changed in 2.3, the gcd will start instantly, while the steady cast will wait until the auto cast is completed. Thus, the time that elapse from the moment you click/the gcd starts until the steady cast begins is: Latency + Auto Shot Casttime.

Multiply test in our german wow-forums confirm: Auto Shot Casttime is reduced by haste.
In example, with no additional haste and BM specc, you're auto shot casttime is 0.5s / 1.15 / 1.2 = 362ms

edit:

The GCD is not affected by latency!
However, casts are.

Note: With a Steadycasttime of 1.5 Seconds and 0.2s lag, you can still shoot 1 steady per 1.5 seconds.