I am a doctor with some altitude experience - and I have some knowledge of diamox (acetozolamide). The first thing I would say is that diamox is not a substitute for careful acclimatisation - "climb high/sleep low" - as per UIAA guidelines. It is no longer recommended to routinely use diamox when climbing to altitude - unless forced to (unavoidably)ascend fast (e.g. rescue worker) - or you know from past experience that you are prone to AMS. If going to altitudes of much over 4000m, expecially if likely to be spending some nights up high, then can be worth carrying some diamox 'just in case' (I have found half a tablet at night relieves troublesome periodic breathing - and at half a tablet, less likely to be troubled with the side effects (tingling, excessive peeing).
I would point out that many feel ill up high due to dehydration - always ensure you keep topped up with fluids.
I would point out that if you are ill at altitude and symptoms don't improve then descent may be safest option, whilst contining to address fluid balance and taking diamox at half to one 250mg tablet twice per day.
If you want to know more then here is an article I wrote on expedition medicine, where the issue of acclimatisation, the UIAA guidelines and diamox issues are all covered:http://www.summitpost.org/expedition-medicine/675753