I agree if want something lighter, I would consider the Salsa for sure. It's quite a nice polycarbonate bag among other things. Except my only issue is that there are a lot of other excellent alternatives on the market and some are priced cheaper (Tumi for example is often on sale and their hard cases are quite good). I admit I bought the Titanium for the showiness, but I have found for some reason it seems slighter better built than the regular Topas, so I guess it's not a total waste.

I, however, don't understand the Limbo. I've seen it in the store and I've seen people use it, but it's priced almost as much as the Topas, but it's not really any lighter (actually I think it might be heavier).