I've had friXion pens before and I've always liked them. They are the perfect pen if you want to write with ink and need to erase things often (or simply want to avoid correction fluid)
Just a warning: because of the properties of the ink and changes in temperature during the shipping process, the ink may come already transparent, making it look like the pen doesn't write although it seems like something is flowing out of the tip. I fixed it by simply unscrewing the pen and putting the ink refill into the freezer for around an hour. Works like a charm now!