Ubuntu 14.04 LTS (64-bit) Trusty Thar personalization

Your options for a Desktop Environment are:

• Unity (Ubuntu default)
• Gnome (3) (install from Software Center)
• Gnome (2) Flashback Services (install from Software Center) - use it with Metacity

You can install all of this and select the one you want to use at login by clicking on the circle icon in the up-right corner of the user selection.

There are several posts helping to make your decision:

• LifeHacker's Linux Desktop Faceoff: GNOME 3 Shell vs Ubuntu Unity helps to choose between Unity and Gnome 3
• This ubuntuforum post helps you customize Unity to get back some of the Gnome2 features you're used to.
• This blogpost helps you customize Unity further.
• This blogpost helps you get rid of Unity completely (this can be risky according to the comments) and get back to a Gnome2 style interface.
• This blogpost helps you get back to a Gnome2 style interface without removing Unity.

My decision is: Gnome (2) Flashback Services with Metacity.