I went to a group stage day last champions (Kru vs PRX, GIA vs EDG, and FNC vs BiliBili), and one at Madrid (PRX vs EDG, and SEN vs TH).
My experience both time were great. It does help when you get to see your favorite team play and when the games are good, but it's still fun no matter what.
Also, the fans make the experience what it is. I have to say EDG fans travel really well, and that GIA vs EDG was just insane to watch in person.