I've test driven it several times and you are right about the blind spot with the top up. On the other hand, I really like the lines with the top up- they did a very nice job with the flying "buttresses."
I live in Houston and had an M Roadster for about 3 years, always had the top down unless it was wet out- didn't make any difference to me if it was hot or cold out- if it was dry, the top was down. Will most likely treat the 6 the same way.
2006 650i convertible: mineral silver, cream beige leather, black top, light birch wood, steptronic, sport, cold weather, premium sound, satellite, Moto V557 w/cradle.