During my short PSC experience with MPower I learned one thing - after each hard crash it's best to fully reflash the BIOS otherwise board starts spitting '55' out on random. Other than that, the experience was exactly the same as, say, on ASUS.
By the way, there is no such thing as new stepping. E1/L1 is just the way new CPU-Z (from 1.64 up, I reckon) detects IB chips.