Martinez put together a very good first 11 in his first season. He had us playing a way we never had under Moyes. Toward the end of the first season other teams worked out how to play against us and we had a poor finish to the season. Then we had two seasons finishing eleventh without any attempt to try a new formation or a different way of playing even though we'd been well and truly sussed out.
Koeman has already started building a squad that is capable of playing a variety of formations. We've played three at the back, a 433 and even the old 4231 which was effective at times. Not only is Koeman willing to change formations depending on who we're playing, he will also admit his mistakes if the game isn't going right and will make changes as early as 25 minutes in. I don't see how anyone can be upset or unimpressed with the start Koeman has made.