First time I had to do it was last year. Fucking pain right up the fucking cunty hole, including several phone calls and being given conflicting information which was not always accurate or totally helpful, and sometimes patronising of me not being able to understand their "simple" system. Once finally at the point of actually being able to submit the figures though, it was actually quick and simple.
Was inevitably late though so got fined, but as had paid no income tax since 1992 didn't mind in effect paying a bit. This year though not so eager. Still lunching it out till last minute tho (as is my way with most things..). Only just read this page of this thread, and its making me think maybe should attempt it some time BEFORE 11pm on Thursday..
As my mate said when I told him it took about half an hour (forgot about the grief before that; and maybe it was more like an hour), he said think of it as getting paid £100 for half an hour's work if I avoid the fine. That's quite good motivation.