Pro Versatile design
One of the most useful features of the Yoga 3 Pro is how versatile the design is. You can use it as a standard laptop, as a tablet and in the stand/tent configurations. The solid hinge means you won't be afraid to move it around to find whatever position feels best for you.
Con Computers may have man-in-the-middle adware installed
Lenovo is shipping computers preinstalled with man-in-the-middle adware called Superfish. It's a web proxy that can hijack any web session, including encrypted/https sessions. And since the root certificate is the same for everyone with private key present on the machine that's now publicly known, anyone can spoof any site to people using Lenovo laptops. Currently, it affects IE and Chrome browsers with Chrome expected to push an update that will block the certificate soon.
Uninstalling Superfish won't remove the certificate.
Lenovo are standing by their choice to install adware.
Con Glossy screen might cause issues in bright environments
Glossy screens are just not good for a work machine, they are meant more for multimedia. So when the ultrabook market is geared towards users who need the portability for work a glossy screen does not make a lot of sense. High lighting situations such as an office (work) or outdoors (portability) create an extremely hard to see screen when they are glossy.