Or a demo could work against them.... people when the play the demo they expect the entire game to be like that and if they don't like the demo they will never want to buy it thinking "Hey the demo svcked the full version can't be any better" So the idea of a demo is a double edged sword.
That's comparable to judging a book by its cover.
A game Demo is more like the descriptive paragraph the author gives about their book to get more readers interested in it.
I know that there is a topic about hoping for a demo but I'm just giving some ideas of what it might have.
1. you can only make one character for either side
2. you will have limited customization (both cloths and guns)
3. you can only play the Container City campain (for all modes)
4. you can only level up to like 3 or something
1. One character for either side sounds good
2. Just to give players a taste, and include the light, medium and heavy body types
3. This Mission from the Media section on the main Brink website and an equivalent for Resistance.
http://www.youtube.com/watch?v=RmKZchM0AiE part 1
http://www.youtube.com/watch?v=T--G56pv-3U&feature=channel part 2
http://www.youtube.com/watch?v=1UWtGCsd_SI&feature=channel part 3
4. Lv. 3 sounds good to allow players to preview some of the abilities and unlocks.