I have a Kona Dew Deluxe myself and used the very same bag from April - December. It's a good bag, although, I learned the hard way one day, that you should NOT rely on the plastic clip alone to secure the bag to the rack. (Maybe that's obvious to everyone but me). One day I had it heavily loaded secured only with the quick click or whatever they call it, and hit a big bump in the road going pretty quick, and it fell off. Ever since I started making sure to use the velcro straps as well and never had another problem.

I had the rain cover too, and it worked well for me.

I did end up switching to the Ortlieb rollers (bought them for myself for Christmas). Mostly because I just needed more space (carrying my laptop, clothes, etc. etc) and really liked the fact that it's waterproof without having to use a separate cover.