My throw-out bearing has been rattling for the past 100k miles. If it is not to loud and goes away with the clutch in you should be ok. If it becomes very loud or squeals when the clutch is pushed in then it needs to be taken care of. Like Paul said changing a through out bearing and clutch is no simple DIY. What is your level of mechanical ability? If you don't know when the belt was changed you may want to change it along with the belt tensioner, and idler pulley. Also check your crank pulley to make sure it does not have any cracks in the rubber.
After getting the car inspected this morning, dude at the service station talked to me about minis. He said he has an 08 MCS with the clutch blown up at his driveway. He mentioned in his quest to fix it, he found that there's a class action lawsuit with Mini/BMW regarding the R53's and the clutch and throw-out bearing issues. He said if I take it to a Mini dealer, that they will fix it for free. His didn't qualify since he has the turbo. Anyone heard about this?
Thanks guys, I was skeptical myself, and I thought if this was really the case, folks around here would have known about it already. Anyway, I have an appt with my dealer this Wednesday. Which leads me to another question, can anyone recommend a good aftermarket warranty? Would that cover the clutch and throw-out bearing or are those consumables like tires? Thanks again, this is an excellent forum!