Valkyrie Profile has always been a bit intense as far as difficulty is concerned (judging only by the original/Lenneth and Silmeria), but that's mostly because it's got quite a few intricacies that they don't usually properly explain, especially in 1/Lenneth. The period system in 1/Lenneth is also very annoying, but it makes the game feel a bit more alive and emphasizes intellectual skill point distribution/proper planning.
Also, of course the music is wonderful, it's Motoi Sakuraba. <3 He is one of the superstars of video game music in my mind, with such a large portfolio of work from so many different styles. The Valkyrie Profile games have especially memorable/brilliantly-composed music, fitting very well with the general setting and fitting the mood exactly. Not to mention the pieces are lovely to listen to on their own.