Hi Andy,

Yes, the attacks rely on grabbing enough weak keys. In general, it is a purely passive attack so if you have low traffic on your LAN it will take ages. I have seen corporate WLAN's where it took a couple of days. Most attackers will see the acquisition speed and give up, unless they reckon you are a very worthwhile target.

In general, I guess it depends on how paranoid you are. I tend to err on the very paranoid when setting security standards for my clients, because then they can lower the level of security if they want but they have some understanding of where they could go to if circumstances require it.