You know you've been playing UT too much when...
...someone refers to actually using a default key binding in UT and you think to yourself "Rookie".
...you calibrate your mouse sensitivity (on another system/for another game) by using a ruler to standardize how the mouse moves to perform a 360.
...your mouse sensitivity setting goes to the tenth or even the hundredth.
...if you can't use direct input, you take note of your windows mouse speed, so you can get your exact UT mouse sensitivity back if the windows sensitivity is changed.
...you find yourself glueing a mouse back together for a friend to get a few more UT games out of it.
...you bring (to a LAN party) or have (at home) an extra mouse, just in case. (or was this one already listed?)
...you get in a debate with your friend over the which keys to bind to which weapons. (proof that your friend plays to much UT also)
...you get in a debate with your friend over how the weapons should be ranked. (proof that your friend plays to much UT also)
...you make assumptions on a person's Shock Rifle combo skills based on how high it's ranked in his/her weapons preferences.
...you map/remap your other FPS games' key bindings to your UT bindings, with the non-UT equivalent functions (such as "Use") mapped in place of such keys as "Best Weapon"--as other FPS games don't use such useful functions, which may frustrate you.
...you host a game, and have settings at an absolute minimum on a 1.4Ghz machine, just to keep the LAN game running that much smoother.
...you haven't replaced that ageing voodoo 3 card, because it still runs UT quite well.
...in addition to thinking UT was smart to have a Windows-similar GUI, you think Windows would be smart to have a more UT-similar advanced settings GUI.
...you wonder if there'll be a mod/mutator to run UT in U2/UT2, in case you like the UT weapons better.
...you can actually post additions to a "You know you've been playing UT too much when..." list that is already way too long.