The biggest downside to not using the ATC is that when using real weather, I can't get permission to land at an airport that is currently IFR only conditions only. I just have to come in to land and hope like mad that their are no IA aircraft landing ahead of me to block my landings, causing me to go around. :(

As CoolP has said, Lou gave us some information along the lines of adding more distance to the TOD if you have a tailwind, and (I think) reducing the distance if you have a headwind (step in and correct me if I wrong Lou!). I don't like to reduce the distance because I am always worried that I might be to high when capturing the ILS and GS.

Mark