I don't like the Guild Battlegrounds.
Why? Because it completely changed the game. To worse.
1. GBG has totally dominated the guild ranking. Now, your position depends on your league and you can do little to change it.
If your guild doesn't participate in GBG, it will end in the abyss of positions 500+...
2. It demands a lot of time. You cannot pop in, do some battles and leave the game, as you can do with the Guild Expedition. No, you need to follow all day what is happening on the map, you need to be right in time when the protections ends, otherwise another guild takes the province and it is blocked for another 4 hours...
3. It extremely favors big and rich guilds. At first, I thought that it favors big guilds only in one way - more players = more battles/negotiations and I thought that a guild with 20% more players would be able to do 20% more.
But things are worse.
The building prices are the same for everyone (they don't depend on the number of guild members), which means that small guilds can afford to build a little, while big guilds can afford to build more. Which means that every single player in a bigger and richer guild can do more than a player in small and poor guild. Even if the single player from the small and poor guild is stronger. What are the consequences? Small guilds will merge or die. Guilds which don't participate in GBG will die.
But if you think that it is the real problem of GBG, it's not. Things are much worse.
How? Let's start with the following questions: How do you think you should play in the GBG? How was it planned by game developers?
I think that most of the players would answer both questions as follows: attack the provinces you are told to attack, do some battles/negotiations, and that's all. How many battles/negotiations? 20, 30, 50, maybe 100, if you are a very strong player. It also depends on which buildings you build.
WRONG!
One of my guildmates has shown us how to do it "properly". If you got 4 Siege Camps in provinces neighbouring to the one you want to conquer, you have only 4% chances that your attrition will increase. Add just one more Siege Camp or Watchtower, and you got 100% chances that your attrition will not change. With high enough military bonus ("high enough" isn't extremely high in fact), you can do auto-battles with no losses, so you can do them practically infinitely. OK, there are building slots, but usually you can have 4-5 SCs in 2-3 neighbouring provinces. Anyway, how does it work in practice? My guildmate has done almost 1000 battles in the first day of the GBG - he was just building Siege Camps everywhere. Our guild was the strongest one already, but spam-building SCs allowed him to totally dominate the map. Nearly alone. All you need to have is: plenty of goods in the guild treasury (and old guilds, which play for years, got them). At some point, spam-building SCs and fighting with zero attrition growth is cheaper than negotiating... It totally destroys the so-called balance the devs have made between fighting and negotiating.
As you can see, the GBG is broken, yet it has a huge impact on the game. That's why I don't like it.