I've only done the Reading half but would echo the comments above, it's well organised and well supported, especially through the town centre. The dual carriageway near the end is quite boring and I've always found it quite tough as it's near the end when you tend to be hanging on.
They've revised the course slightly so the diversion away from the stadium is at the beginning and not the end which was always a bit soul destroying.
The WW50 sounds like it's going to be a muddy slog fest, part of me wishes I was doing it but being shin deep in mud isn't my idea of fun if I'm honest.
I'm back in for the SDW50 again next April and have put my name on the waiting list for the SDW100 but I've got my eye on the canal slam as well, if I decide to take the plunge with that then the SDW100 can wait for another year.