For EUR4 I would buy it. 90% of the time I have Fast Track for most airports I use via status and sometimes I get to the airport and all security points are flowing quickly or no one there so I use the standard one. Other times I have seen terrible long lines and thank god I had Fast Track. For EUR4 I would have it as a back up just in case. Very very tight connection on two tickets so 5 mins faster could be make or break if you run into problems. If everything goes to plan and the check points are all clear then you only lost EUR4 not really big money.