I like the 3e mechanic but don't like how it breaks down at higher levels. Most poisons have Fort DC saves that are less than 18. Well, by 15th level most fighters are going to yawn at that even if they take 2d6 Con or Str damage. Because they know that a little healing or spell will fix them up right away. That's why I use the variant rule we created for
Poisoner's Handbook that does hp damage every round in addition to ability damage. It makes poisons much more deadly and a reason to be feared. It's interesting to watch the party force the cleric to prepare
slow poison and
neutralize poison multiple times.