Understanding that the requirement is acrylic for strength, the rounded corners give me pause. I would imagine that they would be hard to clean without scratching. I've been a glass guy all my life, but up until recently I've only had small aquariums. I got a large acrylic tank, and I was definitely struck by just how EASY it scratches. The Mag Float cleaner I bought (yes, it's the acrylic version) left micro-scratches/clouding in the tank. I now cover it with a microfiber cloth front inside and out to clean it to keep the scratches down.
The issue that I have is the light growing algae on the glass that has to be scraped or cleaned off - I honestly don't know how I'd clean the corners without scratching them, but I've only thought about it for a few minutes now. I bet I'd come up with something.
For the built in sump, you're basically going to have to stock it like a 55 and not a 75 - this has been mentioned before. Also, you'll be limited in beefing up the filtration if you ever need to, so stocking is way more limited in this tank.
I honestly think you'd be way happier over time if you went with a traditional sump under the tank. I get the acrylic for earthquakes, but why the integrated sump design?