Re: Newnovelist, I bought it a while ago and (very) occasionally use it - that's not necessarily an indictment on the software itself, more my somewhat "flighty" nature when it comes to these things - my PC is crammed full of underused software!
It is a useful piece of software for organising your thoughts with regard to characters, settings, etc - especially if you're working on a complex saga with a cast of thousands based in a myriad of places. There is a function to help set up scenes, plotlines, etc. but like PaulW I found this not as useful. For story structure and plot, I personally find the best method to be Word/Excel, with a well-thumbed copy of Robert McKee's Story to hand - but that's just me.
Memnoch - these software programmes can be useful, but (correct me if I'm wrong guys) they only really help organise thoughts - in terms of getting your own original story down, it's going to be down to you and you alone - no software will write it for you (thank god - otherwise we'd all be churning out the same tat which passes for Hollywood plots these days!). Probably the best thing is if you identify exactly what you need the software for - it may be that some of the stuff which you already have (spreadsheets, etc) will be more than good enough.