I have done it quite a few times with no problems at all. Works like a charm and is heaps easier, effective and a lot less messy, than removing the pan. You still have to change the filter, gasket etc. at the recommended interval though.
BTW Nissan Matic D isn't real cheap. I use it in my S3 R31. I got stung around $13 a litre from the local Nissan dealership. But that's in Tassie so I'm not sure if there is extra for freight etc. Castrol Transmax Z is exactly the same stuff but a lot cheaper.
R31Man