The biggest thing for me was drafting - it felt like EU was behind the curve on drafting. Aside from their first losses against MyI it felt like Dignitas was drafting far superior teams to everyone else. The actual mechanical skills were fine, but the drafts... In terms of particular teams:
1) Team Liquid were losing at the draft stage. Possibly because the patch had only hit Monday, but they clearly were not prioritising the right supports at all. Both times in their loss in the quarter final they let Rehgar go through to the enemy team, and then Kharazim was banned so they had to resort to Uther. To me that showed two issues - they didn't understand the relative strength of Rehgar, and they didn't have a deep bench for supports. Dignitas had exactly the same happen, but they just ran Tassadar or Tyrande solo healer and it worked great, but Uther definitely wasn't working for TL.
Seriously, first picking Sonya made no sense at all in that game.
2) Navi had the unfortunate luck of having Dig in their grou, and Dig losing to MyI unexpectedly. Can't really comment much because they lost 2-0 to Dig twice, but it felt like Dig had simply 'figured them out' from practices scrims.
3) Fanatic got unlucky, and to be honest their semi-final with Dig felt like the final. They were in my mind the second best team here. Dig having to beat their former team mates, who they are still friends with, to get to the final was bittersweet - I miss Aetheroangels Tyrael play!
4) MyInsanity were the star breakouts, going further than anyone expected. Their drafts were unusual and I think that gave them the edge, as well as their relative newcomer status - Dig simply hadn't practised against them or for them at all on day one. Will be interesting to see how they improve between now and Kores though - unusual draft choices will only take you so far, as we saw in the final. (that Cho'gall draft was awful!)
5) Dig played well, consistently, and showed a deep roster. I particulary liked their game on Battlefield in the final, where they seems to be playing an aggressive jungle style more than anyone else I've seen in NA / EU. Whilst it's always a map where ganks happen, Dig repeatedly used Shadowstalk to go deep, deep into enemy territory for kills, bypassing walls and forts to hunt someone down which was great to see. Right now they look like EUs only real chance at Korea, but we'll have to see how that works out when the metas clash.
The entire Jaina thing was interesting. EU clearly places a higher priority on Valla's sustain over Jaina's burst in most comps. Clearly they like Valla's flexibility, vault and access to giant killer a lot more than NA - not convinced by it myself, but we'll have to see. There were a couple of drafts in particular where the lack of Jaina stood out like a sort thumb - if you have Stitches AND Lunara on your team not taking Jaina seems mad!