floatation tank! awesome...

Absolutely! Erik is planning to build a floatation tank here in our new house, it fantastic! have you ever heard of John Lilly? very special man, he actually was the one who invented it, and had amazing experiences.
The DR is different, as you already said, because of the long time: a good DR should last at least 14 days. Mantak Chia and Vital don't make them so long because of commercial reasons, but the long permanence is important both for bio-chemical and for psychological reasons. Another very important difference is the quality of the dream state: in the DR you allucinate and you slip inside a deep meditative state, but you seldom "trip". This is somewhat challenging, because you have all this time to fill and all this alertness, the usual activities have ceased (like you cannot read a book or see curezone), so you are finally alone with yourself naked.
Have you been so lucky as to try the floatation tank for indefinite time? that's the main reason we want to have our own, to be able to stay inside as much as the experience requires. Floatation tanks are very expensive to buy, so we have still to decide whether to build it ourselves or to purchase it. And then, at that point, there will be also the great adventure of having DR and floatation tank together. In one DR we made, we were in a place with a swimming pool inside and it was simply amazing to swim or just float in the water (once I also fell in the swimming pool by accident, though! when in DR I use to get lost all the time, even in a small apartment)