Originally Posted by Walker
When you rack the beer too soon, I've heard that this can basically cause your fermentation to slow down to a crawl, because so much yeast was left behind in the primary.
I think that is some what debatable (what isn't in this hobby). While racking early takes the beer off the yeast cake early it will also have more active floating yeast in the beer.
In my personal experience, racking early left me with more sediment in the secondary, which is not a good thing for long term aging, but relatively harmless for normal 2 - 3 week aging. Though that extra trub can be a pain when racking to your bottling bucket. I haven't noticed any slowing of fermentation.
I personally let it go a week or so in the primary though.