I have installed fedora16 recently. I don't like the Gnome3 that my fedora got shipped with. I want to downgrade it to Gnome2 as i haven't used any other desktop environment before. Any knowledge about how to do it ?
Are you clear on the difference between Gnome3 and the Gnome shell? If you don't like the Gnome shell GUI, and prefer the Gnome2 style with the panels and menu, you can try the Gnome3 classic desktop. It should be an option when you login.
The main thing to know about this is that right-click by itself doesn't work on the panels. You will need to press alt + super when you right-click to change the panels. Also, the menu is a little different, but that shouldn't be a problem.
I use Gnome3 classic with Compiz and AWN, which I like a lot. I've tried XFCE, but find it lacking for my needs.
There is also a cinnamon alternative, very neat and non disruptive GUI. The underlying technology is forked from Gnome Shell and the layout is very similar to Gnome 2. It doesn't have much tweaks or extensions available like gnome, but it surely serves its purpose. Here are download and install instructions.
I switched to MATE a few weeks back. It's decent so far, but splitting the MATE and GNOME stuff can be a bit tricky.