Working with multi-family residential projects, we have to create a lot of alternate unit plans. If the alternate unit only occurs in a mirrored orientation from the primary unit, we have to mirror (and copy) the alternate unit outside of the building to create the unit plan in the same orientation. This is not only very time consuming--it also leaves a lot more room for error because when the exterior wall/windows (not included in model groups) change, we have to apply the same changes inversely to the mirrored unit. This might not seem like a huge problem but when you have 80 different unit types and an owner that likes to tinker with units right up until construction, the problem compounds quickly.
If Revit would allow you to mirror views without mirroring the model, it would save an immense amount of time and errors. Please consider this!