I've used a lot of terminal emulators over the years trying to find the best one for my needs. Lately I became lazy and just started using the default Gnome and Xfce terminals but as of today I've started using LilyTerm and am kicking myself that I didn't switch sooner.
LilyTerm is a lightweight, fast terminal emulator with an attractive and very usable GTK user interface that blends in well with Gnome and Xfce, and if you your window manager supports composting LilyTerm supports true transparency. It's a really polished app.
Instead of a menu bar that takes up screen real estate or narly xterm or rxvt
.Xdefaults text files, you configure LilyTerm through a simple right click menu that shows you the results of your changes as you make them, and allows you to save them for future sessions.
A table without a tablecloth
To show why LilyTerm is Win, I constructed an entirely subjective comparison table showing the other terminal emulators I've used in a productive capacity over the last few years. The difference in performance between xterm and rxvt is noticable on older hardware, but not on my current ThinkPad.
Build it and give it a try :).