With my book, Weaver's Web, I ventured into series territory for the first time. The rest of my books stand alone. The character arcs are self contained, and if I turned them into series, I would destroy my carefully constructed arcs, or I would hold them in an ugly gray stasis. With Weaver's Web, I had more story to tell, simply, than when I got to the end. But I admit I didn't plan it that way, and still have to plan the next two books.
All the same, I'm a stand alone fan. That's why I write them. Stand alones create compelling, self contained arcs and plot. I find serials, in general, end up with static characters, or they Jump the Shark. The original concept of the series ends up destroyed in order to further the series. Instead, however, it kills the series.
So give me a shout--my few commenters--and weigh in.