Couple of changes:
Stupor is a better version of Mind Rot since it involves discarding two cards, but one of those being randomly chosen. It has the same mana cost, so it'd be a no-brainer to use Mind Rot when I have a couple of these babies.
Smallpox doesn't always play well. It's a great card, but since this deck runs a somewhat limited collection of lands, it usually ends up crippling my game. I've moved two out of three Smallpoxes to the sideboard and replaced them with 2x Geth's Verdict, since some creatures can prove to be troublesome SOBs when playing with this deck.
Black Cat isn't that good of a 2-drop. It can be a nasty little deterrent against attacking, but it just doesn't seem to perform well. I've removed three of those and, replaced them with the third Stupor and 2x Oona's Prowler which can put my opponent in a rather uncomfortable situation where he/she would have to choose to take 3 damage or discard 1 to 2 cards. Either way's fine by me.
With future in mind, I've been thinking of using Raven's Crime. This would give the deck a bit more longevity in sustained play, not to mention it'd make mana flood a lot less irritating. Additionally, Distress could be a viable sideboard card, considering that it could get rid of any threat opponent poses.
