I am using the CalDigit FASTA-6GU3 here as well and it is working fine in my 5,1 Mac Pro. I have the eSATA ports connected to my RAID-5 backup system and a Voyager Drive Dock. One of the USB3 ports connects to my RAW STEEL memory card reader, and I use the other port for portable disk drives occasionally. I am seeing no delays or sleep issues with the eSATA ports here.
There is another long thread here discussing this card along with others that you may wish to find and read. The CalDigit does require a USB3 driver (not using the native OS X driver), and apparently can't achieve maximum speed with 2 ports active due to sharing of the controller (not really an issue for my application).
Another popular card are the USB3 only (no eSATA) Orico cards which do use the native drivers, however the 4 port card requires additional power cable to function.
I needed a single slot solution for both USB3 and eSATA, thus my use of the CalDigit card.
I'm using the CalDigit FASTA-6GU3 as well with OSX 10.8.5. Generally speaking I'm happy with the card. It works great with USB3 hard drives. I've had random driver related issues with the system "crashing" but it's honestly only happened a handful of times.
I've had bluetooth interference issues with the card that I've documented on the forum before. Have a GBU521 installed on my keyboard and it works fine now with the Apple mouse, but the random issues really did not go away until after I installed the Logitech M510 mouse, dongle and drivers. It seems at that point the Apple mouse started actually using the GBU521 correctly. I had disconnected the internal bluetooth, but was running into boot issues after installing a GTX 680 and reconnected it to eliminate a possible cause - never disconnected it again.
I'm hopeful when updating to 10.9.x no additional issues with arise. It seems to use the same driver for both 10.8 and 10.9, but I cannot 100% verify that.