Anders, I used to do that, and it's not a horrible play if you are that sure on your read. Keep in mind, he does not have to be holding AAxx for you to still be a potential dog or roughly break even. This means that your read doesn't really have to be 100% that it's AAxx he's holding (although you can usually tell, i.e. you raise 5x the bb and he comes back with triple that - he almost certainly has AAxx).
I think there might be a time, depending upon the opponent, that you can lay down a weak AAxx hand like AA9K or whatever. It probably comes up around once every 30 billion hands or so. Sure, you are a big dog to a monster:
http://twodimes.net/h/?z=2243604
pokenum -mc 500000 -o8 ad ac 9h ks - ah as 2h 5s
Omaha Hi/Low 8-or-better: 500000 sampled boards
cards scoop HIwin HIlos HItie LOwin LOlos LOtie EV
Ks Ac Ad 9h 57054 65935 147827 286238 0 0 0 0.334
As 5s Ah 2h 147827 147827 65935 286238 252401 0 0 0.666
But you really need the read to end all reads to lay this down profitably. Many guys will come over the top with hands like A23x where you are about 50/50:
http://twodimes.net/h/?z=2243617
pokenum -mc 500000 -o8 ad ac 9h ks - ah 2s 3h ts
Omaha Hi/Low 8-or-better: 500000 sampled boards
cards scoop HIwin HIlos HItie LOwin LOlos LOtie EV
Ks Ac Ad 9h 156659 309330 188725 1945 0 0 0 0.468
Ts 2s Ah 3h 188725 188725 309330 1945 266761 0 0 0.532
Shortstacked I call every time. Against a tighty I do the same, especially if I think I can push him off on the flop.
If you are talking high only then the odds are pretty similar.