Quite simply one of the most beautiful places I have ever been to. Well worth the 90 minute drive from the capital. After wandering the upper streets and taking in the breathtaking views you are then rewarded with a well deserved Karlovacko beer in one of the many bars on the lower street. I'd especially recommend Bar Sanda.
I have to also mention the sunset from Captain's Club in Banjol (just a 15 minute coastal walk from the old town).