Several improvements have been made to the LDX GUI under Jessie. In tinkering with it, a crew from the Raspberry Foundation literally rewrote LDX to be smaller in size and faster while fixing a few bugs and adding a few features. In rewriting it, they are calling it "PIXEL" - Pi Improved Xwindows Environment Lightweight.
 
They also added Chromium (which I do not agree with as it is geared to the R-Pi 2 & 3 and not for the older/single cpu-core models), and the SenseHat Emulator (Useful if you have the SenseHat for the R-Pi). There are a few other tweaks in it as well.
 
Pixel will be the default GUI for Raspbian in this and future releases (Which I also do not agree with, one should be able to load that GUI they like and not be stuck with one). You can download the updated Jessie with Pixel on the R-Pi website. The new NOOBs, which you can download, will have Pixel installed as well.
 
Here the link to the article:
https://www.raspberrypi.org/blog/introducing-pixel/
 
Thing is this - I do not know if it will run on the older R-Pi. I'm guessing that it will. I do know that Chromium will choke the older models: A/A+, B/B+ and the R-Pi 0. But the other browers are available on the system though they have to be accessed through the text console to turn them on in the GUI.
 
They claim that Pixel is lightweight, so it should fit and run on the older R-Pi's. If anything, with a firmware update (which I need to post up), it should run on the older R-Pi's, especially on the R-Pi Model A & B.