I have one, it's crazy bright. Simple Velcro mounting may not be ideal for some but so far it has done much better than my hotshot for being seen.

No rack mount can be a hassle, I'm able to mount mine just using the velcro and so far so good.

I haven't really looked at how visible it is during the day at a distance but plenty of comments when I walk away from my bike of "hey that crazy taillight of yours is still on". At night it's pretty nuts.

I'll really put it to the ultimate test over the next several months leading up to then actually riding in RAGBRAI. Be using my wiz20 for my bar light probably as well since I can carry spare 18650 cells for everything and done.