Based on experience following Nokia's N-Gage brainstorm (it's a commercial version called uservoice but practically the same thing) the most important goal is to have regular updates that really are regular updates.

The people running the brainstorm should try to agree a plausible interval (perhaps once a month) where there's time to investigate bugs and features so that a proper reply can be given to each suggestion.

The N-Gage uservoice site's big problem is that the updates just didn't come regularly, sometimes there would be updates and sometimes there would be months with no word from anyone.

So basically, a guaranteed update once a month is better than a not-so-guaranteed update once a week.

The other important thing is that the people doing the updates must have the ability to get official statements from the people in charge of whatever needs fixing or enhancing. If Nokia and others refuse to talk to the people updating the brainstorm, then the brainstorm will be useless.