Is there an Clutch Inspection hole on TT like the Boxster's? - on my friends 01 Boxster 2.7, you have a side view of the disc friction material through a 3/4" hole in the bell housing, seems like a good way to determine wear.

Perhaps another way to determine clutch wear is the amount of fluid that migrates from the the clutch master to slave cylinder - I noticed that in the 17K miles that I have driven my TT (from 4K - 21K), the fluid level has dropped from full to midway, anyone corrolate this to clutch wear - for example, top off fluid to exactly the FULL line when replacing clutch and note the level when clutch starts to slip (due to wear, not glazing, etc). This could potentially be a great way to literally "see" the friction material being worn away.

Bond