The Asus VivoBook S551LB is definitely a good 15.6" ultrabook. It's powerful and well finished, has extensive connectivity, long battery life and decent sound quality.
Best of the rest
Apple MacBook Pro 15" (2013)
This year's MacBook Pro 15" is one of the best laptops we've reviewed for this form factor. Anyone who loves quality images will love this computer. Our only qualm with it is the limited number of connections ports. Everything else is great... if not perfect!
Gaming On The Go
Asus Republic of Gamers G750
The Asus Republic of Gamers G750 has loads of connectivity, high processing power, a quality screen and great speakers, providing a top-notch laptop gaming experience.
HP Pavilion Sleekbook 15
The HP Pavilion Sleekbook 15 is thin, powerful and affordable. It's perfectly suitable for most activities, although it's not great for gaming. It has a good range of connections, decent battery life and reasonable amount of storage space.