I spotted quite a few differences between the actual COTA layout and the maps that were published before the track was finished.
Compare this picture with either the Google Maps view on the track or the Lotus recon laps.
The beginning of the Esses, namely T3 and T4 are less tight, while T8 and T9 are a lot tighter. Also, the two left kinks between T14 and T15 are less tight, and finally, the last two apexes of the T16-18 sequence are less edgy, more streamlined in reality compared to the preliminary maps.
Sorry if this has been brought up before.
I like the less tight T3, T4, and particularly the kinks between T14 and T15. The latter allows for quite an unusual line between the two hairpins, noted by Ant at the SkyPad as well last weekend. I think the T16-18 modification is less important and generally neutral. On the other hand, I really dislike the way the Esses tightens towards its exit. I liked the preview configuration better – quick in, slower in the middle and quick out. Now its even quicker in, slower in the middle and even more slower out. I think it breaks the rhythm of this otherwise glorious track.