I've been riding my mundo as my daily ride since august, I do about 100km a week running around and across town to go to work, run errands, trips to the beach at the weekend. Sometimes I have very little cargo, sometimes quite a lot. The mundo is, in my opinion, a great ride and the perfect bike (for me) for utility riding. It's geared good and low so I often climb hills spinning while sat down, and the only time I really notice the weight is....going downhill, coz it accelerates real fast.
Even did a bit of off-roading in the local park yesterday, it was kind of fun.
Overall my experience is: don't be put off by the weight, I barely notice it. Do be encouraged by the cargo capacity: it's great to be able to pick something up on the way home (like some lumber- saturday morning that's exactly what I did!) and not have to worry about whether it'll fit on the bike or whether the bike can take it. With a mundo: it will fit on, it won't break the bike, and you'll be able to ride home comfortably (even uphill - Okinawa is a hilly place).
And no i dont work for mundo, I'm just really happy with the bike (V2 mind)