First off, Adam's biological dad's big scene. While I get the desire to have him turn up, the scene doesn't feel as nice as it does in the book where it's a subconcious move by Adam. In the series he's all 'you're not my dad', but the book made the point much better: Adam is told that his dad is coming, immediately assumes it's Mr Young because that's who he's viewed as his dad all these years, and subconciously warps reality to make it so he appears instead of Satan. Especially as, like everything, it paled before what the book made me think of when Satan was mentioned, which was a majestic, beautiful, and commanding figure to fit with one of the novel's themes.
Which brings me to my second point. If I may quote the book for a moment
Originally Posted by Good Omens, by Terry Prachett and Niel Gaiman
Demons throught the series are presented as relatively ugly, filthy, and generally unpleasant looking, which is not how they're presented in the book. The book, as the quote shows, makes a rather big deal of heaven and hell being incredibly similar, building up to that final point where to the ordinary observer they might as well look exactly the same when going all out. I'd have prefered it if the demons had been at least somewhat more subtle, wearing suits or at least clean clothing, and going more for a 'fallen angel' look than a 'middle ages peasant with extra disease and flies' style.
Anyway, I don't think I can safely go further on that
topic. Plus I'm shattered.