Don't know if your latest update (cheers, by the way) already includes this, as I haven't gotten around to try it, but here's my instinctive thoughts:
If alcohol can be used to restore sanity without restrictions, there's the potential of scummy/boring tactics where the player finds a "safe place" to get drunk every now and then. Perhaps it would be more challenging if drunkenness only makes you more resistant to losing sanity and/or just restores sanity that was lost up until a few rounds ago. So you'd have to drink just before or during encounters with nasties to get the sanity benefit. This way, penalties to combat etc. would be more interesting.
I've no personal experience with opium as such, but my rule of thumb would be that getting high in creepy catacombs writhing with nameless horrors isn't necessarily good for your mental health. I know opiates are great pain killers, but at least one person I spoke to who got it administered in the hospital got "weird dreams", which the nurse said was not uncommon.
I do like the idea of opium raising magic awareness, though. One adverse effect (reflecting addiction) could be that you get less apt at magic when you're sober: If you rely too much on drugs to get "in touch", you might start losing the ability to access that side of yourself when your blood is clean. Anyway, I'd probably poke around here for info about opium:
http://www.erowid.org/chemicals/opiates/opiates.shtmlAs always,
Minotauros