I've connected the camera, wifi, gps and a usb hard disk to the pi at the same time using a powered USB hub (Belkin I think?) and haven't had any problems. This was with mains power. But you're right, there are many people who have run into problems. Either I was lucky or I didn't notice them.
I think connecting a keyboard and mouse as well may significantly increase the odds of it failing, which is unfortunate given how the Foundation advertised it.