LXQt is the Qt port and the upcoming version of LXDE, the Lightweight Desktop Environment. It is the product of the merge between the LXDE-Qt and the Razor-qt projects: A lightweight, modular, blazing-fast and user-friendly desktop environment.
Quote from LXQt site
The next release of Lubuntu (an Ubuntu flavor) will not be shipping with 14.10 as the default DE (Desktop Environment,) instead it will be sticking with the current, GTK-based, LXDE. This may be considered strange by some, as lately there hasn’t been a whole lot of stable features released for LXDE, mainly having to do with the file manager.
However, the reasons behind this decision make sense and the added time will allow developers to add features and make the software even more stable and user-friendly, as well as adding a buffer for transfer to Qt5.
LXQt migration discussions for Lubuntu aren’t entirely on-hold for the current release cycle. Discussions regarding what apps using Qt should be ported with 14.10 are underway, while separate ISOs for testing and getting LXQt into official repositories are being developed.
To add the PPA just run
sudo add-apt-repository ppa:lubuntu-dev/lubuntu-daily
followed by the typical sudo apt-get update and sudo apt-get upgrade commands.
However, with these instructions come a word of warning, these builds come directly from the Lubuntu git and are daily builds and as such are not stable and should not be used in any production system.
If anyone uses Lubuntu or LXQt, please share your thoughts below!