Thomas Shey
Legend
Actually, in light of my previous post, there's something I'd like to add to my general "unnecessary complexity" list: errata.
As a rule of thumb, if your errata runs to more than 1% of the page count of the book you're fixing, it probably means you've made a mess of writing the thing. If you need to patch the same thing twice (that is, provide errata for your errata), that almost certainly means it's unnecessarily complex. And as soon as your "errata" moves beyond fixing errors and to revising good rules, you're adding unnecessary complexity - it should almost certainly wait for the next edition.
There are exceptions to all of the above, of course. And, of course, it's all IMO only.
Unless you've got a big playtesting budget, its all too easy for a game with lots of moving parts to show problems in various places you never saw during initial design. I honestly suspect that if you kept the complexity of games down to the point that wasn't a potential issue for most game companies, you'd have to wipe out half the market once you got away from WOTC (who may screw up just as often, but can afford said big playtesting budget).