I can say that I enjoy a scenario that is not a "rail shooter", but that drops enough clues to be able to follow the storyline. This is not always ever easy to do.
As for the first question. Yes, I like extra frills a lot, one of my problems with a (good) scenario like Two Strands was the lack of such frills. On the other hand they often take much longer to make a good storyline and can bog down the production of the scenario quite a bit.