It has been several years since I have been on the Royal Princess, but there is no way I'd ever hesitate to cruise on her. She has a very loyal clientele and was the 'forefunner' for many of the newer ships designs.
She has a great layout, with outside views from every public room except the conference room/theater. Yes, she is old, so there is no way you can compare her with something like the Grand Princess. Some of the features (such as bathroom fixtures, etc) may appear older.
I first sailed on her from Athens to Dover in May 1997, the again on the Baltic RT Douver in May 1998.
I am looking at sailing her again in March 2004 from Santiago to Fort Lauderdale.