We opted to tile not only up to the ceiling, but also tiled the ceilings themselves over our showers and tubs. Even though we used very good quality paint (Aura matte in the guest bathroom, Aura Bath and Spa matte in the other two), we wanted to really minimize the chance for any issues with the ceilings (in the wet areas), eg.; mold, mildew, peeling or cracking paint....

At the very least, I would tile up to the ceiling. IMO, it's a sleeker, "cleaner" and more modern look (as you also said). That said, I have seen some beautifully done bathrooms with the tile ending a foot +/- below the ceiling so I'm sure it would look good if you went in that direction instead.

FWIW, in our one bathroom with glass shower doors, we did NOT take the glass to the ceiling either. We did go with slightly taller glass than we might have; mostly because the bracket location would have been right in the middle of our mosaic border tile, but an added bonus for DH was the fact that the taller glass made any water over-spray less likely to occur (doubt it would have happened, but it made DH happy! LOL).

Go to the ceiling! So you don't have to worry about water damage and painting in the future.

Wow. It was only after I posted this picture and saw it online that I came to the realization that I'm really, really tired of those faux finished walls. Had them done 15 years ago, and it shows.

So now it's an easy decision. I'm going to paint the walls a solid, soft, silvery grey and tile the shower walls all the way to the ceiling.

I think you'll be happy with that decision. I was hesitant to the ceiling in our remodel this summer, but we had so many issues with water damage it seemed the prudent choice. I'm very happy with the look (though we do have crown moulding over ours as well).