def - thanks. If/when IB recognizes the more favorable margin rules, I'll take a look at IB again. Right now, I may be looking at having to split my personal/corporate trading and a couple of IRAs between different brokers (one who recognizes the newer margin rules and one who allows option trades in the IRA). So if IB will support both soon, it'll be a convenience advantage.
IB has other advantages in this regard that aren't necessarily obvious. When you close a position you've held overnight your buying power is restored immediately. Most other brokers lock up your funds for a day. IB manages this because they self-clear. (Which is probably the main reason that they can offer such low commissions too.)