Well, all I can really tell you is what worked for me. when I was originally looking to build my system I wanted a video card at least as powerful as a GTX 580. After reading some reviews about how two HD 6870's in Crossfire bested the 580 in most games for about 2/3 the price I went for it.
With the HD 6870's in CF Micro stutter was noticeable, sometimes very noticeable. After reading about a possible solution I gave it a try. I created a 4GB Ram Disk, disabled the paging file an all other drives and dedicated the entire Ram Disk to a Paging file, except for the tiny amount win 7 requires you to keep free.
This has completely eliminated all Micro Stutter as well as the occasional dropouts where my frame rate would almost bottom out (worse than a Micro Stutter).
The program is called "Dataram RAMDisk v3.5" and it's free as well as being completely certified by windows for Win 7 64bit and many others.
So yes, there is a greater risk of Micro Stutter with 2 cards. How bad of a risk depends on your system and choice of cards but, that doesn't mean it cant be dealt with.
For the solution I outlined you do need to have an extra 4GB of ram to dedicate to the Ram disk and even then I cant guarantee it will work for you, Just that it worked great for me.