The recent download that you have seen was an effort to fix the graphical problems that many of you witnessed. It was later noticed that there may be problems directed solely to AMD video cards, which was just confirmed. For those of you with AMD cards should see a fix early next week. (Update, this bug was resolved in version EA4.14)
As for the recent large downloads; we all understand that large downloads are not easy for many of you who have slow or limited internet connections, however, during development of a game of this caliber things like this happen from time to time. We all do our best to test these updates before they are even released to the public, but this was one of those times that we did not see any problems with the build. The reason for the large downloads were because all of the aerial imagery was replaced with newer, better versions, and so that the internal format could be changed to provide users with more efficient releases. This was a lot of files to replace, and this issue with the Steam upload combined with the graphical issues it had to be pushed out a second time (if the first time wasn't bad enough) so we apologize for that.
Throughout early access we also can't guarantee that this won't happen again, but we ask for your patience while the flight simulator of the future is developed.