I would stick to Olfa or Fiskar blades. I just read a review of those Improved cut and people were having issues after the 2nd or 3 use of a blade. If you search Amazon, you can find some good deals on Olfa blades. I bought a 10 pack of Olfa 45 for a good price.
As far as the cutter itself, I prefer the OLFA 45mm Deluxe Handle Rotary Cutter, which has the retractable blade and ergonomic handle.