How effective has it been for you?
** I had an officer pull up next to me at a stoplight and tell me he could see my bike from 4 blocks away (about 1/3 mile)

How visible is it? Can it be seen by others during the day? Please describe.
** I run it during the day. It's not as impressive as at night, but it makes me feel better going from areas of sun to areas shaded by trees, knowing that I've got my blinkie on.

How well does it hold it up?
** Hasn't broken so far

Does it get affected by rain?
** Not that I can tell. I used my all through last November, and we got 15.3 inches of rain that month.

How often would I need to change the batteries?
** I use mine about 1.25 hours a day, 4-5 days a week, and I get a couple months out of a pair of batteries.

Where and/or how many places could it be mounted?
** Seatpost, chainstay, helmet clip, backpack, rack trunk, any blinkie loop...