I had a coaster brake bike for a couple of years, but jettisoned it in frustration. As mentioned earlier, the inability to put your pedals where you want them is a real impediment, and wheel changes and chain tensioning can be a chore. But mostly, I thought the braking itself was terrible.
IMO, coaster brake bikes are perfect for beach cruising, but are a needless handicap for anything resembling real-world riding conditions.