Steps to reproduce:

1. Maximize a gnome-terminal, there should be like 140 rows and 60 cols.
2. Start a python interpreter and type "import random; import string; print "".join(random.choice(string.ascii_letters) for x in range(50000))"
3. Press and hold enter. 

Text will scroll hackisly. It is not smooth at all. Do the same thing in an xterm. Scrolling is extremely smooth.

Although this is a stupid example, the same effect is apparent when using gnome-terminal for everyday uses if it is very large. Like 238 rows and 70 cols. The larger the terminal area, the more hackish scrolling becomes.