My friend (who drove my manual) with a 2011 DCT M3 said he didn't hear any noise from his trans.
I test drove the new 911 with 7 speed DCT and it shifted great. Porsche converted this transmission into the first 7 speed manual for a car. I didn't have the chance to drive the 911 manual. I'm sure the R8 will be fantastic. A bit pricier though.