- What you read is not what you get: Gamescom is technically a trade fair and maintains a separate area for press, exhibitors, and other "trade" visitors. The new Skylanders game was based in the trade area. Neither SWTOR nor GW2 were on the floor. Marvel Heroes was not on the floor either, though David Brevik personally made up for that by hosting a fan gathering at the end of three straight days of interviews. Point being, you can show up and not get any closer to the real news than you would have been from home.
- Entrance at the cost of experience: Gamescom claims over 300,000 attendees annually. They do this by selling tickets to the limit of what German fire code permits, and then re-selling the spots of people who leave the show as space-available afternoon tickets. As a result, there isn't really quiet time at the end of the day when you can avoid the worst of the lines. Instead, most lines have matter-of-fact markers indicating that you will be waiting 3 hours from this point. I'm sure it's lucrative for the organizers but it's not a positive experience to walk the floor at 1:30 PM and feel like you have to line up for something now because if you wait any longer the show might close before you can get to the front of a line.
- German is the primary language: You won't have trouble ordering food, as most signage is also in English, most employees speak English, and English is definitely the second most common language. The Assassin's Creed demo had English voice acting and German subtitles/instructions. The WoW expansion trailer had German voiceover, but many of the Heroes of the Storm character trailers were in English. Lego Dimensions apparently flew in a developer from America, who would hand off the mike to the German community guy periodically. Just be aware that you will probably miss out on understanding some of the content if you don't speak the language.
- German Public Transit, Also German: (Also, I found the public transit system hard to use because you need to identify the right stop to know what to pay and then find the right train and not stay on too long and end up on the other side of the country.)
I don't mean to be too negative on the show - in some ways US shows like PAX suffer from the same crowding issues. You do get a very large crowd with all the requisite cosplayers (note: unlike in the US, German cosplayers can use realistic looking guns without running afoul of law enforcement), merchandise, and access to the top games for the fall if you were prepared to wait. I was coming from England, and tacking this onto a family vacation, so I'm mostly okay with the effort and expense. I would not have been happy with the effort and expense if I'd flown in from the U.S. Your mileage may vary.