So, wow. The desk staff was excellent, she was perhaps one of the best desk staffers I've seen in Europe. The room was very clean, & the view of the runway & all the big 787/747/A350's is PRICELESS. It's also unimaginably convenient, and she even gave an extra pillow!
The only thing I would change? I felt rushed to leave by 8/0800 the next morning. My flight wasn't until 1/1300 so an 11am-12pm checkout would have been PERFECT. Maybe they offer longer stays but I didn't see that option nor a late checkout option & it didn't seem busy on Monday night at all, so that shouldn't have been a big deal. Compared to most hotels I didn't stay there very long, & it feels you have to leave @ 8am, no other option offered. The cost was higher than other FRA airports so they should do later checkout.
However: I walked out of the hotel & my flight was literally at the nearest gate to the hotel, it doesn't get better than that for convenience. No going through security twice, just: security, connection, sleep/eat, next flight. **I would advise all staying to get meals at their previous airport or when they get to Frankfurt, before or after passport control, the food options are limited in Z, & nonexistent after 9pm/2100.
As far as the hotel I'll give it 5 stars merely for the literally unbelievable convenience of location. This hotel makes Frankfurt (FRA) far more traveler/business traveller friendly and I'd definitely stay again, only change: I'd request longer stay well ahead of time.