Since the patch, my old macro isn't working correctly anymore..

old macro:

/dismount
/stopmacro [mounted]
/cast [modifier:shift] flying mount ; summon dreadsteed

That doesn't work anymore.. it always gets past the stopmacro step. It would appear that the dismount in the macro changes the 'mounted' state right away. (I wonder if that's a bug?)

new version is

/cast [modifier:shift,nomounted] flying mount ; [nomounted] summon dreadsteed
/dismount

which appears to work, except on rare occasions where it dismounts me and still tries to summon up a dreadsteed. (ie. I'm on a flying mount, activate the macro and it dismounts and starts summoning)

Yes, in 2.1 /dismount and auto-dismounting via spell cast is effective immediately.