Hello, in Blender 2.4x I used a lot Ambient Occlusion, with the option “Sub” (the other option is “Add”).
In Blender 2.5 there are “Add” and “Multiply”, but “Multiply” gives different results (worst in my opinion) than the old “Sub”.
Is there any workaround?
AO in 2.5 just darkens, as it should.
Env brightens up the scene.
Indirect Light adds the color bleeding and light glow.
That is pretty much the way how it works.
with distance and factor you can now decide how much the AO darkening affects your scene.
Hope this helps.
You didn’t read my post.
2.5 darkens, in a different way. That’s all.
Basically the problem is that “Multiply” darkens (relatively too much) illluminated objects, without darkening at the same level objects already darkened by direct shadows. 2.4x was better.
Edit-
It’s not true that 2.5 AO just darkens, the option “Add” still gives light to objects. It seems equivalent to the old “Both” (Add and Sub).
In 2.4x I almost never used the ‘sub’ option and later on opted for multiplying the AO pass combined with the shadow pass in the compositor (making a multiply map that didn’t darken areas brightly lit by a sunlamp or other bright lamp).
This produced a somewhat flatly lit image to start with, but the multiplying added quite a bit of depth, I used this instead of subtract mode on the AO because subtraction mode tends to discolor or oversaturate parts of the scene.
Faxrender, you’re right, but the new way is the “standard” way: ambient occlusion is intended for self-shadowing calculation, not to add GI to the scene. For this in 2.5 you have to use environment lighting instead. After the render refactoring the old AO has been properly splitted in two separated tools, avoiding the weird/hackich old solution of 2.4x. BTW if you need more control you can easily use renderalyers and do compositing to achieve your result choosing the proper blend mode for AO/EnvironmentLight/whatever you need …
Hope it helps.
I read your post well,
I only tired to tell you that in 2.5 the elements are separated and with maybe
a little setting tweak you get 1:1 results.
In my test scenes actually they were the same with add while only multiply in
2.4 was darker.
But again energy and distance settings help here.
So, why in “Ambient Occlusion” they left the (useless) “Add” option which adds light to the scene (I never used it) and removed “Sub” which correctly darkened the scene using self-shadowing calculation?
At the moment the only way to darken the scene is the “Multiply” option, which works worse than the older “Sub” option. That’s all.
well the question is if this is already a finale version or still an unfinished work in progress.
if you turn of AO and turn on env light you will notice that it also looks
like AO.
Claas
Basically if someone doesn’t know how to use something it doesn’t mean it is useless 
I’ve already explained everything in my previuos post. Please try to understand what Add or Sub or Multiply means (e.g. googling for “blend mode”), and try yourself to make via compositor the blend mode you are missing 
It can be very funny and powerful, believe me.
BTW if this is the nth complaint thread about 2.5 in alpha stage, then I deeply apologize: my only intention was to give support (also if this isn’t the right section of the forum).
Peace.