Remember that 802.11b is a very simple signal type. 802.11g is a more dense data encoding for more bandwidth on the same channel size. 802.11n, is a multi-channel use that allows up to three channels to be "bonded" into a single stream. On 2.4Ghz, that allows about 3 different APs to be active without interfering with each other. On 5ghz, there are many more channels, so that you can get many more APs up and running, interference free.
On 2.4ghz, you have bluetooth, portable phones, VCR rabbits, baby monitors, and many other types of user devices which can create interfering signals.
It appears to me that Lion is having problems "recovering" from interferring signals. That is, if you have a great network, you see limited issues because you don't have things happening that cause the WiFi layer to report errors and keep trying to recover/make things work.
But, those that are reporting continued problems, no matter what, and then buy a "router" and/or "switch bands" or "switch technology", seem to illustrate that when there is a problem network, you can switch your network type and have good results.
This would be why people switching to the old driver no longer have problems (those that it works for at least). Either the old driver is not reporting the kind of error that the new one does, or it is not reporting anything up the stack to the other layers and so it stays working fine with the old driver. If you've tried the driver and it doesn't work for you, then perhaps you don't have "The Lion WiFi Problem", and you need to look at a different level of the network for your issue.