I first started shopping around for a different terminal emulator after finding I had a lot of work to do in the command line interface and gnome-terminal was not the best environment in which to do it.
In my work I use cli (command line interface) applications such as Midnight Commander, Htop, Irssi, Links, and others on a day to day basis.
Gnome-terminal is a fine application, and I have no ill-will towards it's creators. I find it perfectly suited to occasional usage.
One of the drawbacks to terminal emulators like gnome-terminal are that universal keys like f10 are not passed along to the cli application, because they have been reserved for use by gnome-terminal.
Programs like Midnight Commander and Htop (just to mention a few) use the f10 key for closing out the application.
I also enjoy Terminator's ability to separate the screen into other terminal emulations. This allows you to have Midnight Commander, Htop, Irssi and Links to all be open simultaneously. With this feature, you can quickly copy information from one of the programs and paste it into another, making cli work much faster.
I also enjoy the drag and drop feature.
In conclusion, I think that anyone that has to work often in the terminal will appreciate this application.