Those are some slick rotors...
How's the brake feel and overall experience with those?

Actually it feels completely stock. You don't hear or feel the grooves, which is a good thing. A can't say that braking performance is improved significantly, but it does help to sweep the dust away.

Maybe I'll go with cross drilled instead of grooved rotors instead. I suppose grooves offer more cooling or something more performance wise instead of daily driver feel.

Just avoid drilled if you do any track. Drilled rotors have a tendency to crack.

Did you go with Stillen slotted rotors, or another brand?

The Stillen rotors didn't exist yet, these are StopTech 1 piece.