Well a friend of mine has downs syndrome and loves to play halo, however because of his disability he was not able that good at the game and often needed help even on the easy mode in campaign. he disliked multiplayer because in halo 3 although he tried his hardest he could rarely rank up because he wasnt up to anyone elses standard, this made him feel worse about himself. in Reach however will play multiplayer because he ranks up through having a go and trying his hardest and gets other rewards such as armor.
there is a seperate area for those who care about stats called the ARENA where you get but in different divisions based upon your skill, etc.