The only negative I can think of is it makes your BC pretty heavy. Depends on where you're diving, I guess, but when I'm diving in cold NorCal water with a ton of neoprene and lead, it makes switching my BC to a new tank a little bit more cumbersome. That said, I wouldn't go back to a belt for the world. It's infinitely more comfortable to have the weight in my BC instead of around my waist.
The cons mentioned above don't really apply to the ranger. You can dial in your trim with two weight pockets on the tank band, which can be moved up and down. The main pockets rest right above your hips and, for me at least, this is the perfect spot for both trim and comfort.
Should you lose one of the little yellow pouches, they can be replaced for a fairly nominal fee (you also don't REALLY need them - I forgot them on a dive trip and took some shears to a defenseless mesh bag and made some ugly but functional makeshift pouches).
Oh, and the DUI system does look like it might be the best of all worlds. I have never used one in the water, but have tried one on in the shop and it seems like a great (albeit expensive) solution.