Greetings, luther.

I'm using Knoppix 7.2 and just the following in rc.local now:
sudo iwconfig wlan0 txpower 5mW rate 54M key (key code) essid "(essid name)"
Time to browser on-line is 50 seconds, same as when using Win7 on this laptop.

FWIW.
1. sudo is not really necessary as Forester has pointed out.
2. Klaus K has changed the 7.2 boot up process somewhat to improve boot time,
but I'm not aware just where and how.
3. The reduced transmit power was a suggestion of Klaus K's to counter-act
local wifi interference. I don't know if this helps on time to connect
but it seems to improve the frequent disconnect situation here.
4. It's quite likely Network Manager has improved as well since this thread
was initiated.

In answer to you question, I suggest the following:

As root call up leafpad and edit /etc/rc.local
by adding the following line just before the "exit 0" line:

iwconfig (wifi's device name) rate 54M key (router key code) essid "(router essid name)"

If that doesn't improve things, then this might be one more reason
to benefit from upgrading to 7.2.