rolls the hips forward, and for me personally i tend to lose my balance, but thats just me

Posted under another comment as well: Try to focus on "packing the neck" or "keeping the chin tucked" rather than looking up. Keeping the cervical spine in alignment will make you more stable and less likely to injure yourself. Looking up isn't the end of the world, but may compromise the neck in the long run, especially under heavy loading.

IronChild, the airpipe is a reverse L shaped "hose". Looking up straightens the "kink". On the other hand, the cervical spine (part where the upper back [thoracic vertebra] and the posterior cranium connect) forms a loose C curve. Looking up exaggerates the C curve and compresses the cartilage lining in each vertebra.