I don't want to go too over the top with praise for Koeman yet, I seem to remember phrases such as 'he's a breath of fresh air', 'his clever substitutions are winning us games' and 'a top club will be in for him at this rate' (or words to the effect) being used in Martinez's first season.
Having said that, the early signs are good. He's improved the main things that were missing the last couple of seasons, ie fitness, defensive organisation and we look good at both defensive and offensive set pieces.
He's as straight talking to the media as you'll find in a manager and he's got the blend of slick passing football when possible, but if in doubt get your laces through it and reorganise. Happy so far