Should I buy ECC or non-ECC RAM?

While prepping my new machine for 'Longhorn', I had a decision to make - Should I buy ECC or non-ECC RAM?  ECC RAM costs a bit more but by not that much. ECC RAM are a necessity on servers and have now trickled down to (high-end) workstations, granted there are some performance losses (very marginal at best). Oliver Aaltonen's excellent Unofficial FAQ about the Dell PowerEdge 400SC series has a very informative explaination on why ECC RAM is certainly worth it. By the way - if you are a Dell PowerEdge 400SC owner, I highly recommend Oliver's website (and support it too).