Tried shaving with one of these in my new (to me!) Slim last night, and it felt like I was trying to shave with a butter knife. The blade was so dull it felt like it was ripping the hair out of my face. Didn't even try the blade for more than 2 strokes. Finished shaving with my Tech and a Treet Classic. I don't know if I got a dud blade or if that's just par for the course with these. Anyone else tried these blades before?