I've literally just finished watching the last six episodes of GitS SAC 2nd GIG and at the moment haven't watched any of GitS in original language/sub format. I feel that on first viewing, watching any of GitS as a sub would have left me a touch bewildered.
Having complex story lines and detailed dialog. I think anyone trying to follow the dialog and on screen action simultaneously, would be hard pressed to take it all in in one viewing. Probably taking three or four viewings before you could confidently follow the action with out concentrating on the subs too much. But thats just my opinion.
My personal preference is to watch as a sub, as the subtitles tend to give a better representation of the story, where as the dub tends to reflect the market it is aimed at and changes certain aspects of the story to soot that market. As a whole I endeavour to watch everything in it's original language, but where I feel watching something as a dub first would be of benefit, then I will do so.
I recently watched Tenchi Muyo OAV in original language/sub and can say that I'd be happy to watch it as either sub or dub. I prefer some of the English speaking voice actors, but find the translation (sub) to make more sense.
Something that does annoy me, is the exclusion of the original language/sub track by certain distributors :cough: Sony :cough: then having the balls to charge extra for a special edition that includes the original language track.
Now to go and re-watch GisT in order - SAC, SAC 2nd Gig, Movie 1 & 2
SSS will probably find it's place between 2nd Gig and the first movie in terms of it's time line.