Interestingly I did a trip to Holland earlier this year and flew a few days around there. It is now mandatory for all traffic above 1200ft to have Mode C. That is all traffic apart from gliders.
So even with the TCAS in the Cirrus it remains paramount to keep a good lookout.
It is very illustrating to go and fly in a TCAS equipped machine and find out how much traffic you miss even when you do your best to keep a good lookout. Even when the TCAS points out to you where the others are it takes some good looking to see it against some backgrounds.
FD