On our first Princess cruise (Grand in 2003) we waited 15 minutes for a table for 2 only twice. Yes, some passengers were upset. However, instead of hanging around the dining room doors stewing (or, worse, yelling at the headwaiter), we just grabbed a glass of wine and listened to the classical music in the Atrium. The time passed very quickly and peacefully. We knew the food wasn't going to run out before we were seated!
On our second Princess cruise (Golden 2004) we never waited for a table... and we ate in the Bernini dining room between 7:00-8:30 p.m. 5 nights out of 7. Our menus were exactly the same as the ones traditional diners had. We had no complaints about the service, either.
It all depends on what you want out of a cruise. We like to hang loose, which means (among other things) eating whatever we want, where we want, and with whom.