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.
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 Weak CPU
A 4K Ultrabook that struggles with 1080p video. Issues with multiple tabs open in Chrome which tends to use the CPU near 100%. The quick price drop on this product bringing it way below 1K shows how poorly received this device had been and it is mainly due to the under-powered CPU being used.