soil Indoor soil mix advice?

[Dave2000]

The faster the drainage the less the compost can absorb surely? Especially when it's become hydrophyllic I would think slower drainage would be better than fast.
 
I mix all compost plants with 15% fytocell (EU thing) and I would not use anything else. At a push states side maybe a little perlite for aeration but normally I would mix nothing (If I can't get the fytocell). I prefer to drip feed though which eliminates all issues of hydrophyllic compost and gives a good time for wick action to evenly wet the compost and bring new air into the root zone.

 
Slower drainage isn't necessarily better unless the soil had an excessive amount of sand or other non-absorbant material in it.  If there is enough water that it is running out of the pot it is an excessive amount and it is then best for the soil to return to a lower moisture level as soon as possible, but the issue isn't about whether it is 2 minutes or 5 but rather whether there is a near blockage of the drain holes so it's a few minutes versus several hours.
 
Otherwise, ideally a plant pot will never receive enough water that any drains out,so the water soluble nutrients aren't washed away.

 
Linda Chalker Scott, Container Drainage. She's a bit of a drumbeater, and I don't agree with a number of things she tries to "debunk", but there is some good reading on her "Horticultural Myths" section. "Tapla" from Gardenweb, has a multi-thread page on Water Movement that is a much better browse.
 
The jist of it all is that root health and water movement against gravity are much better served by a homogenous media.

 
Edit:  Great wall of text deleted.
 
Her article ignores the relevant factor which is that it's not drain rate itself that matters as much as preventing drain hole blockage.   A controlled test is great for demonstrating the particular set of variables used but can't be used to make the sweeping generalizations she did when water rate, soil density, drain hole # and size, etc. change.  People didn't randomly start adding gravel and other materials to pot bottoms, rather it was a response to seeing poor drainage and that these materials did improve drainage in many situations. 
 
To ignore direct observation of the result would be madness.  Sometimes it helps and sometimes not.  The times it doesn't are generally when the soil is already too high a density to start with so silt and clay migrates down towards the holes.  The solution then is a soil change not a bottom layer.