I recently changed brakes on a 2000 Grand Caravan. I just used the cheapy brakes (standard). I used proper proceedures... bled the brakes, kept the fluid full to prevent any air getting in the lines... but when I finished and took it for a test drive, it stopped VERY poorly. I thought I had done something wrong or gotten air in the brake lines.
After driving it (carefully!) for about 50 miles, it started getting better. After about 100 miles, there were working like they should. Sometimes brakes need to be burnt-in for them to work properly, but I've never had any take that long before.