Just a word of caution from my friend at BMW, Dinan is not part of BMW. He says that anything that is modified by Dinan is not covered under factory warranty and if you have a problem with your car and they find that it's caused by a Dinan product, they won't cover it. Here's what the Dinan warranty says on their website...

"If your vehicle is currently covered by the vehicle manufacturer’s new car limited warranty, Dinan products are warranted for the remaining term of the vehicle manufacturer’s new car limited warranty. The manufacturer’s new car warranty is limited to 4 years or 50,000 miles (80,000 kilometers in Canada), commencing on the date of first retail sale or the date the vehicle is first placed in-service as a demonstrator or company vehicle, whichever is earlier. Dinan’s warranties are transferable when ownership of the vehicle into which the Dinan products were originally installed is sold.

To obtain service under this warranty, the vehicle must be brought, upon discovery of a malfunction or defect in materials and/or workmanship, to the workshop of any Authorized Dinan Dealer, during normal business hours. Proof of purchase in the form of a lawful invoice is required. The Authorized Dinan Dealer will, without charge for parts or labor, repair or replace the defective Dinan component(s), as well as any original vehicle manufacturer’s component(s) that may have been directly affected by a Dinan component, using new or authorized remanufactured parts. The decision to repair or replace said parts is at the sole discretion of Dinan and/or the original vehicle manufacturer. Parts for which replacements are supplied under this limited warranty become the property of Dinan and/or the original vehicle manufacturer. In all cases, a reasonable period of time must be allowed for warranty repairs to be completed after the vehicle is delivered to the Authorized Dinan Dealer."

According to my friend, it get hairy when a problem occurs and Dinan says that it's under the factory warranty, but BMW claims that the problem was caused by the Dinan mod, so it's not covered by BMW, then you're SOL. It won't void your whole warranty, just the part that has the problem. Here's some info from SEMA that addresses that issue. Currently, there is only the exhaust, throttle body, and CAI for the 4.8is, so there shouldn't be too much that is voided.