I used a few 285HV's in this manner. My experience with the cheap umbrellas that are included in the kit are pretty bad... I replaced them with the also cheap Wescott reflective Umbrellas from Adorama. Not sure why Strobist recommended the shoot-throughs.

The stands are OK. A couple Nalgene bottles with some cord held the stands in place when it got breezy for me. When the power of my 285HV's wasn't enough in a 2 light setup, I doubled them up into one umbrella, which worked quite well.

Depending on what flashes you're using, I recommend doing some kind of external battery pack, too, as they're less fiddly than changing AA's all the time. Even homemade ones out of NiMH cells in a small enclosure wired into dummy batteries will work well.

I tried using my backpacking headlamp as a modeling lamp one, and the LED's definitely are not powerful enough in open shade. I think the output of my headlamp is around 200 Lumens, which is powerful than most of the affordable bike LED lights.