I can relate to so much of what you guys are saying. When I first started atkins, I was losing weight wonderfully, but I felt like utter crap all the time, and eventually I developed heart palpitations and dizziness.
I felt like this for 4 months.

Now I know the reason I felt like that was because I was so addicted to carbs and my insulin was so out of wack before, that my new low/normal levels of insulin were messing up my electrolyte balance. Insulin plays a role in regulating potassium, and combined with the diuretic effects of restricting carbohydrate AND losing weight very fast (which is potassium wasting), all this equalled to an electrolyte imbalance. The electrolyte imbalance and dehydration made my heart rythms irregular, made me feel dizzy, and generally feel like crap.

Eventually your body will adjust to your new healthy insulin levels, and as you progress everything will go at a slower pace thus preserving electrolyte balance.
However, what you can do right now to make yourself feel better is buy a potassium based salt, or supplement, and use it. Make sure you drink A LOT of water, it is very important.

I feel soooo good now, but then I felt terrible. Don't worry guys, it gets better as your body adjusts. Just remember, the harder the adjustment is to this new way of life, the more you need it.