I'm not sure where non-round speakers first got a bad name. I'm guessing the first non-round speakers were relatively immature models that didn't perform well, or maybe oval speakers have a stigma of being "oem" so therefore they must be junk.
I think oval speakers are mature enough now that they perform well and they can get you more cone area in a space that wouldn't otherwise be practical. For example we make a 6x9" woofer that fits in the top of the saddlebags on motorcycles.
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These speakers make excellent use of the available space and I've been tuning something similar with stellar results.
I like them for the most part since you can get more sound out of a similar size hole. They can be tricky to simulate in terms of off-axis response for all of the discussion you're having above though. Also, oval speakers require more sophisticated tools to model the off-axis frequency response and by more sophisticated I mean more expensive and sometimes time consuming. I think non-round speakers are mature enough at this point that they offer a solid deal and they are starting to catch on as a way to get a "bigger" speaker in a similar space.
I also get tripped up on the 5x7" ovals because that's a common size to print photographs which is another hobby of mine!