Just walked out of the theatre. Will write more later but - first reaction? Underwhelmed. That just didn't hit the mark for me at all. Certain scenes had their merit, granted. But overall... A bit disappointed. Wow. Was not expecting that reaction... Anyway that's just my first thoughts straight out of the door.
edit: Another observation in terms of visuals. May be considered spoilerish ...
Very impressive. The Klingon vessels looked magnificent - they really evoked a bird of prey. However, one interesting tidbit - if you're like me and dig a bit of space combat - you've seen it. The trailers contain about 90% + of all the action. So don't get your hopes up in that regard.