I would agree that wireless isn’t quite ready for all uses. If you have highly sensitive data, it’s never a good idea to send it over the air via a radio – that’s never as secure as sending it via wires.
WLANs are also just not as fast as wires. .11n is pretty quick – just as good as 10/100 ethernet if you’ve got everything setup correctly – but it’s not as fast as gigabit ethernet. Not a big deal if you’re just browsing the web, but it does really matter if you’re moving large files around the LAN.
My expeience is that in some buildings it just doesn’t work properly.