The best weight belt system I have ever tried is one made by a company in South Africa called Bright Weights. They are also sold in the USA, I think through a company in Florida, although they are sometimes hard to find. You can also get a whole system, which includes ankle weights and tank weights, and I like all of them a lot.
The weight belt (as well as the ankle weights) is made of nylon webbing, but instead of threading the weights onto the belt, there are loops that you put their weights through. This makes it easy to add or remove weights, without having to take apart and rethread the belt, so it's fast & easy. The belt uses a stainless steel buckle, and you ditch the belt the same as any other. The weights themselves are short little cylinders, and the way they are set up makes them really comfortable, even though they are hard weights. The weights are epoxy-coated, so they don't leach lead oxide into the environment or onto you. The separate tank weight system is also nice because it also functions as a tank carrier, and keeps the tank from rolling around when you lay it down.
I have one, but like I said, they are hard to find. It took me quite a long time to get one, and I ended up buying one from another individual (don't know where they got it), not through a store. Rodale's gave them a great review, which I completely agree with, so if you're interested, maybe they can tell you where to get one.
I really love this belt, it's all around the best one I've seen -- but the weights are in metric. Converting the metric weights into pounds is not too hard, though. (1 kg = 2.2 lbs)
Just so you know, I am in no way affiliated with this company or any store that sells them (like I said, I had a hard time finding them.) I just think it's a really great weight belt system because it's much more comfortable than hard weights, much easier to deal with, and much more adjustable and environmentally sound than soft weights.
otter-cat