It has always worked perfectly with every device, including my MBP with snow leopard, iphone, and other pcs in the house.
My neighbours' wifi does not reach my house so I doubt that could me the problem.
The problem exists only with Lion, infact I've gone back to snow leopard and it works flawlessly.
Probably it depends on the wifi chip installed in some macs.
Mine is a late 2009 MBP