Powers might not change the gameplay of quizbowl that much (I don't think more than 1% of games, if that, would have their outcome changed if powers went away), but they make quizbowl more fun and enjoyable, especially for newer players. They do this without detracting from tournament quality or gameplay quality for experienced players.
As a mediocre player who didn't play in high school, I actually disagree with both parts of this. The addition of powers encourages a bit more risk-taking on both sides and throws more uncertainty into games...I've always noticed many more negs on powermarked sets, whereas at ACF Regs this year I remember most of our games featured one total neg, if at all. (I can totally see your argument if you think this is too few negs!)
I think opinions on ACF powers depend heavily on general attitudes toward negging and risk-taking in quizbowl, which I feel are progressing towards the positive, due to the relatively few people still active who did not play NAQT sets in high school. I particularly enjoyed ACF Regs this year because of the lack of negbait and good middle clues that stopped many fraud answers (for the most part). Had powers been instituted on the Regs set, I think we would have seen many more negs and not more powers; however, had the set been less well written, the power incentive could lead a more aggressive but not necessarily more knowledgeable player to fraud an answerline early.
Furthermore, I've always appreciated the dichotomy between ACF's strict, academic, distribution and longer, more objective questions, and NAQT's more whimsical answerlines and cross-category clues. There seems to be a movement in quizbowl to narrow this divide to make ACF more accessible to NAQT high school players, but I actually think for those new to quizbowl as a whole in college, ACF's formats make a lot more sense with regard to straight-up knowledge. For me, it's more rewarding to get a middle clue on an ACF set out of power than to devalue that middle clue on a powermarked set because
it's out of power.
That said, I think there's a place for powers at the Fall level, especially if the set is written like it was this year, with short questions, strict difficulty control and clues accessible to both players straight out of high school quizbowl and new collegiate players. I do think powers add a level of "fun" to a set at a lower level, but at higher levels and longer questions, where middle clues are far more important than at early levels, they just add more frustration and incentive to neg, which has never been ACF's style.
Again, this is just my (probably unpopular) opinion, but I'm wondering where some other people who started playing in college stand on this issue, besides Eric and Conor.