[Jaruzel]

Some OSs (I'm looking at you Windows) can get 'sticky' and refuse to fail over to the stronger AP even if it does have the same SSID and passphrase. The only solution is to force disconnect and reconnect the wifi on your device, and even then it doesn't fix it all the time.

I've found the most 'reliable' arrangement is to not only have the same SSID and passphrase, but to have them all on the same frequency and if you can, make them all from the same vendor.

Also, if you are going to re-purpose an old router as an access point, make sure you turn everything off on it except the access point service. It mustn't hand out IP addresses or offer any DNS resolution. You want your devices IP to be provided by the main router regardless of which AP you connect to. It sounds obvious, but this the main stumbling block people encounter when trying to do this.

[lmns]

Some Windows wifi drivers offer an option for roaming aggressiveness. I think I've seen this with some Intel cards.