The issue I'm having now is everyone rags on the mission builders for making the long briefings- but yet then they get in there not knowing the full story and get annoyed when things don't go the way they want. Sigh.
I don't mind the mission brief's as long as I have the time to read them. I believe though that falls on the responsibility of the player. Sometimes when I get on I have a fixed amount of time to play and I don't want to spend alot of time reading the brief. Thats when I would opt out of playing a new mission...and stick with a mission I was familiar with like Ishot or Back to School.
However a good well planned brieffing adds to the immersion and really allows you to mentally get involved with the game. (example) Your not going out to kill some tanks near or around a town (no read brief). You are actually going to rescue a community of people from evil genocidal maniac who is intent on ethic clensing (read brief). The briefs also give us politcal background as well all of which helps make the sim more real in the virtual sense.
Good briefings are awesome but they must be read in order to get the full effect of the mission. Briefings should be detailed but the responsibility to read them is in the players hands and if a player is having problems getting a mission complete without reading the briefing tough (I am guilty of this). READ THE BRIEFING!!!
I like a nice clear mission brief so I understand whats happening and where, some mission briefs I have seen are terrible and lack any important information so I like it when someone puts some effort into the breif.