They are a good addition to the game, yes. They can be interesting. But custom challange scenarios should be filterable.
Its easy to make a fleet, then limit all counters to it. This can turn it into a boring mirror match. It seems most people like to do this. Create a fleet with weakness, but remove those from the game.
Thats great and all, but i dont want to play those.
To illustrate my point ive set two custom challanges.
There is Impossible! Lenient, which limits very little, but engine speed is 1% and you are against missiles.
Then there is Impossible! Hard which i think is impossible except for mirror matches. All things except what i used limmited, 1% engine speed. Only cruisers. If you play them, you should put your fleet as forward as you can, and come back in a few minutes after 4x speed. Id be very supired is a non tribe fleet beat me here.
Id love to hear any replies, and play and counter challanges.
I might make another one with a bit faster engines, so not to bore us all to death.
Tl;dr : Filter custom challanges!