Filters for the 24/3.5 II

For many years I've been shooting only with only one filter - 77mm B+W MRC CPL, mostly on my 10-22 - and was happy. However, lately I've been feeling a need for ND and GND. The CPL can act as a 2.5 stops ND but it's not always enough.

Now that I have the 24/3.5 II I thought to myself: I'll buy 82mm ones and add a 77-82 step-up ring when I use them on my 10-22. So, I ask all those who use filters with that lens, which filters do you use and what is your impression? Also, I guess a slim version is a must, right?

Happy shooting,
Yakim.