They're probably prohibitively expensive and I'm not sure that throwing ever larger capacitors at the problem is a good solution but supercaps and ultracaps can store a lot of charge.
We tried using a pretty large amount of capacitance. The thing to remember is that we need to build this into a little stickminer that will go in a USB port, so we can't drown it in caps. Overall we've been fairly dissatisfied with this chip so using a different controller is not a bad plan. We have another project utilizing a very similar controller so we already have some confidence in the design.
I think we've spend more time dicking around with this ridiculous regulator chip than the rest of the design combined. It just won't handle the burst current, even at fairly low end starting frequencies. We slapped another regulator on there and it worked all the way up.
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novak