I dont think they are a waste of money, yes even a thatchem approved one like the one I have, can be removed in around 17 seconds by a pro - but that coupled with getting into the car, disabling the ammobliser, getting the armor guard off all adds time - and noise.
The more things you use the more likely someone will try another car.
I guess house alarms are also a waste of money? Well yes they are because everyone ignores them - however statistics show that someone will normally target a house that doesnt have an alarm.
If you want to be really security concious, then have tracker, and have a monitored house alarm.
But I would have though the visual deterrent of having a steering wheel lock is better than nothing at all.