So what, you think Apple engineers are sitting around thinking, "Hey, we got their money, no need to fix the problem!"
Unfortunately WiFi reconnection problems have been cropping up from time to time for quite a while. There have been numerous updates for Leopard and Snow Leopard where the technical notes states that improvements and fixes for WiFi were included. In fact, I think that was true for 10.7.2
One very important fact to keep in mind is that while WiFi issues are sometimes related to the operating system, in other cases it is the user's environment that is the cause. So if your wifi problems exist no matter where you try to connect there's a good chance it is software. But if your problem exists in one specific location the problem could be with that router, how it is configured, or interference from other devices.
One of the things I really hate is when a customer walks in complaining about WiFi problems (without bringing in their base station) and the computer connects to our network immediately and doesn't drop. Obviously they're having a problem but when I can't replicate it we have two unhappy campers - them and me.