NOT TOO long ago, when you dialed an online broker you entered voice mail from hell--that is, if you got an answer at all. "Press one if you'd like to open an account," a typical voicemail menu said. "Press two if you'd like to hear about our new no-fee IRA After you finally navigated to the point where a broker was supposed to pick up, you were often left on hold half an hour, while the stock you wanted to sell kept falling. Naturally, things got infinitely worse when the broker's Web site crashed. But our fifth annual survey of online brokers finds that lengthy waits for brokers to answer the phone have virtually disappeared. Lousy trade executions have also become a rarity. ...