Does the content of an AES Key matter?

I've been looking around for and AES key generation algorithm, slightly concerned about 'what' my key was, and more concerningly, are there 'strong' and 'weak' keys?

Had found a python article which specifically not to use an algorithm similar to this when generating a key:

import random

key = []
for x in range(16):
    key.append(chr(random.randrange(0,255)))
return key

I get the idea that a key shouldn't be predictable, and I know that normal 'random' byte generation based on time isn't exactly random.

My question however, is that even if you do use a simple algorithm (or even a 16-byte passphrase for that matter) for the key and AES is implemented properly, is the key any weaker than any other?