the sp3 is still working as normal like when it was with the maroo. It does get a bit warm after running videos from youtube but on maroo its warm too, and the fan was hardly audible the whole time. Mine is the i7.
And the casing does have vents on the top of the sp3 (when in landscape mode) with mesh for protection against dust and water.
Trident case is one of the microsoft's partner so i don't think microsoft will approve it if the casing cause the sp3 to overheat. I could be wrong though, but its the only hard case that allows the usage of the built in stand and assess to microSD port.