I've just been doing some research on the TTRS, and it seems like a decent piece of kit.
It seems the only real issue is that the Haldex is FWD biased, which leads to understeer - but seeing as Haldex is computer controlled, and you can already have haldex systems reprogrammed - I'm sure that needn't be a problem for too long.
However, once you have the remap and the haldex reprogrammed, whilst you have a very capable car, you'll likely have no warranty.
It seems the only real issue is that the Haldex is FWD biased, which leads to understeer - but seeing as Haldex is computer controlled, and you can already have haldex systems reprogrammed - I'm sure that needn't be a problem for too long.
However, once you have the remap and the haldex reprogrammed, whilst you have a very capable car, you'll likely have no warranty.