Not really any info on what exactly happened or what dangers resulted from it. People may want to change their passwords, just in case. I did. I agree with the sentiment here: This is unacceptable from one of the most-visited Web sites in the world. I hope they explain how this happened and what they're doing about it.
itechreport seems to think this wasn't so bad and there is no need to change passwords, though earlier they were suggesting changing any passwords that were the same as your Twitter account.
And there’s no need to panic now or change your passwords. Twitter has confirmed the DNS records were “temporarily compromised” which means user data wasn’t touched and the “hackers” simply redirected users to their own website.
I've never seen a reason to switch to Voice over IP. The sound quality isn't as good, it's not really much cheaper, you may have to change your existing phone number, you don't have a phone if there's a blackout, and (for some VoIP services)