Today, the Commander Rules Committee announced two rules changes and added a card to the banned list. While the original post at MTGCommander.net is down, a text mirror is available here.

The changes are as follows:

The text mirror goes into detail on these choices. On Prophet:

Casual groups haven't been able to work around it and problematic play has not dropped off in hoped-for ways. Instead, the primary approach has been to steal it, clone it, run it yourself, or get run over. Ultimately, it seems the card is too perfect - it does everything U/G Commander players want to be doing and it does it in a way that makes counterplay difficult.

On mulligans:

We promised in the last update that, with the advent of the Vancouver Mulligan, we'd be evaluating the mulligan process in Commander. This announcement is the culmination of that research. After examining several popular options, and coming up with a few of our own, we've concluded that the Vancouver Mulligan (with the standard first-one-free in multiplayer and a scry once you go to 6 or fewer) is the best option.

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Finally, it’s not an official rule, but we recommend setting aside the hands you're mulliganning away until you get a keeper. That saves shuffling time, and we're all for minimizing shuffling 100-card decks.

And on Rule 4, which discusses mana production:

Being able to generate colorless mana more easily in Commander wasn't going to break anything. But, it represented another "gotcha" moment for players, who were now likely to learn about Rule 4 when someone exploited the colorless loophole. We could paper over it (both "mana generated from off-color sources can only pay generic costs" and "you can't pay a cost outside your color identity" were considered), but a lot of the flavor would be lost in the transition, defeating the purpose. Without the resonant flavor, Rule 4 was increasingly looking like mana burn - a rule that didn't come up enough to justify it's existence.

As with all rules governing Commander, different play groups will react differently. What do you think of these changes? What decks and Commanders get better?