Nokia's internet tablets do it right

The one problem with "continuous scan" like the tablets do is that since not every network shows up every scan, the tablets just don't get the list right when you're in the Connection dialog. Sometimes your network will be in the list, other times it wont. You really do have to build up a list of scan results, just because wireless is by definition unreliable. This is precisely the reason why having a "Rescan" button doesn't work; just hitting the button won't necessarily show your AP.

You could walk through your saved list and probe-scan each AP in the list, but that actually takes a while, especially if you have 5GHz support (lots of channels) or a long list of known APs. So that doesn't work well either. Yeah, there are tricks you can do like probe-scanning the 5 most-used APs, etc. But in the end you have to find the balance between getting it right most of the time, and not getting it right the rest of the time, and somehow making the user not angry.

The user isn't going to blame the air, they are going to blame your device when they can't find their AP... even if the AP itself is a PoS, which is often the case. *That's* what makes wifi hard.