Without intending to add to the bilstein / monroe debate, I would add that I recently took a trip to CG to get my suspension looked at and sorted.
FYI my car is a C4S, 95,000 miles, and was on the original monroes and set up horribly.
Chris said that whilst accepted opinion is that the Monroes should only last 40,000 miles+ he reckoned they could be OK. Sure enough when he looked at them, he said he thought they were serviceable. Bear in mind I was prepared to shell out for new Bilsteins......
Basically the weight distribution had caused the rear shocks to drop - Chris added spacers, tested and adjusted everything, and now the car drives like a dream. Of course they could go any time, in which case I am back to square one, but I thought it was worth mentioning anyway.
FYI this is my second C4S and the first one was uprated and lowered so I have something to compare it to. I dont think the harshness of the ride was an issue for me, but perhaps the tramlining is related to ride height?
On the other hand there are probably plenty of you with lowered suspension who dont have these issues so it is probably down to the setup - I am sure if CG had looked at my old car I am sure they would have eliminated the tramlining! I was really impressed with them.......