Remi, as you've started this thread I'll repost my opinion here;

the forums should be joined together (for example - all adobe software into adobe forum) - when a visitor sees a "busy" forum it persuades a visitor to post. If you put some food in different dishes in different places it won't be the same as if you put everything in one big yummy looking dish
If you have 4 posts a day in 6 forums - it looks barren. If you have 24 posts in one forum it looks busy and appeal to people post more (no many want to post if there are no previous posts).

That's the main and most important thing that should be changed, in my opinion.