If you can find a store near you that sells them I'd advise you to try them on first. I found that RYKA's run small. I normally wear an 8 but I had to get an 8.5. They're wide in the forefoot, which is supposed to be more accomodating to a woman's foot shape, but I found them to be a little too wide. I didn't get the lateral support that I needed, esp. when I do Cathe's hi/lo. I had to put hi-impact inserts in my sneakers to make them fit correctly because after a few workouts in these sneakers I noticed my feet started to ache.
I know a lot of people, including Cathe, love these shoes. But they don't seem to fit me well.