Caustics? How Memory intensive? Do they work?

I haven't yet purchased C4D XL, but I'm interested in the "Cautics" feature. I have tried out the demo and as far as caustics are concerned I only get "out of memory" messages. Since the demo is non-saving, it's rather a pain to set up caustics, and in all likleyhood I'm doing it wrong anyway, my question is: has anybody gotten good results they'd like to show?