I have the version with i3-4000m cpu, without dedicated graphics. Runs well with Windows 7 x64.
Ubuntu 14.04 (actually haven't tried it with the main edition, only Xubuntu, Kubuntu and Ubuntu Gnome ed.), in both x32 and x64, experiences random freezes, that can be solved only by a hard reboot. Ctrl-Alt-Backspace doesn't work, even if enabled, nor does Ctrl-Alt-F1 to switch to another virtual terminal. I saw a post where someone claimed it happens mainly when downloading. It may be so, but I'm unsure (last time, under gnome shell, it did). Maybe the newer bios update, the one for Windows 8.1, from the Lenovo site solves the issue. I haven't tried it.
Also, the Broadcom wireless requires proprietary drivers - they can be easily installed from the Additional Drivers GUI (or something similar) if connected to a wired network. If not, the can be installed from the bcmwl-kernel-source* package present in the pool directory on the installation medium (where there are also its prerequisites, in various subdirectories).
The intel integrated video works flawlessly.