OCZ's XMP modules while quite fast really don't bring anything more than a few extra points to the table in terms their performance. While it may be nice for some users not to have to worry about overclocking the memory manually, this is where we managed to get higher clock speeds. When we went over the 1600MHz barrier with the XMP enabled, it seemed as if the system wanted to keep the timings too low and resulted in BIOS stalls and OS boot failures.
XMP is just another term for the EPP and SLI memory that NVIDIA uses, and really, how many people actually use this stuff? I don't because it really does restrict overclocking abilities. Yes fair enough if you don't have time to do it manually which is ok for the more novice crowd, but consider this - Who is going to be using an X38 motherboard in their system? Most probably extreme users who have more than the basic knowledge on overclocking and how to set their own systems up.
Overall the overclocking was good, performance was high, and the ability to sit back and let the memory do its own work in conjunction with X38 is nice. However, a bit more work could be done for speeds well above the 1600MHz line to give it lower latencies and higher voltages to accept true overclocking, not just lowering latencies.