Coincidentally X58A-UD3R was the motherboard I wanted (it was my first choice), and now I am using it (X58A-UD7 has specs that is too high).
There is no problem with SATA ports. Only from the operating system side, if you connect it to the port that supports SATA 6Gbps and set it to AHCI, it will appear in SAfely Remove Hardware as if it is external device (as the nature of AHCI: hot swappable). If this is annoying for you (I found this annoying too) It can be solved by running commands in cmd / adding registry.
USB3.0 is working OK for me.
I am using 12GB, but my config is 2GB x 6
About RAID, I never use it since I don't think I need it, but from reading the manual, setting it up is easy.
This motherboard supports SLI for two or three cards. the bridge for both 2 and 3-cards configuration is included. I currently use one GTX 465. I would advice against this motherboard if you plan to use PCI since you have to choose between PCI or your second graphic card. In this case, probably you have to choose either UD7 or UD9.
Which other posts you are talking about for issues with SSD on SATA 6Gbps port?