Speaking as both mod and player, I like information in the biography that's pointed and tells me about the character, but I don't like it to necessarily be long. I don't need it to be in a perfect story format, I just need to know the information, and sometimes if the information around the details is too well, descriptive? Not the right word. Anyway, it's possible to lose the important bits in the prose.
I usually try to focus on the important things. If the character has a massive fear of death, either why, or when did it first come up. Turning points in the character's history, where if things had gone differently they wouldn't be the same person. Moments of realization or great change.
Also, as a mod (and as a player) anything that has no bearing on the current game isn't necessary to me. I don't need a list of pets the character had when he was seven or their first best friend if those aren't either in their life now, or impacted their life in some irrevocable way.
But I also know I'm a LOT more minimalist than a lot of people out there, and some of it has to do with my style of play (develop in play, rather than develop ahead of time). And because of that, sometimes I fear as a mod, if I see a truly over-detailed character, that the character won't be changing during the game. And part of what I love to run is a game with strong character arcs for plot.
Not sure if that helps at all, but I figured I'd give the other viewpoint. :)