When starting Terminal in SL it can take up to 20 seconds for the cli prompt to appear. Terminal also frequently hangs while executing remote commands via ssh.
~/Library/Preferences. Move that file to the Trash and restart your Mac.
Also, check for available disk space.
Right or control click the MacintoshHD icon. Click Get Info. In the Get Info window you will see Capacity and Available. Make sure you always have a minimum of 10% to 15% free disk space at all times.
Deleting the preferences worked for a short while, but the problem has returned and the Terminal takes roughly 10 seconds to give a prompt, even when it's the only app running. Plenty of disk space - 47 gb.
This behaviour has only started since Snow Leopard.