I haven't toured on a Big Dummy. But I have a friend who toured from FL> OR two years ago on a big dummy, he was moving out to OR for some time. Essentially it's just a long frame all welded as opposed to the X FreeRad.
I love touring on my GT Rebound converted to an Xtracycle (GT-X). I bought this bike back in '99 as a hardtail mtb:
Through the years my needs for this bike changed, so I retrofitted it into a rigid trail tourer for touring 350mi. on the KATY in MO and to southern MO for a bird surveying job in the forest and after the tour for hauling groceries, garden tools and supplies with a inStep child trailer that I bought cheaply:
It was an excellent multi-surface touring bike in that form...but this year my needs developed further. And touring in MO gave me confidence that I can easily travel cheaply all over the US (the world?) with my GT. But I now needed my bike to tour/move around the country/work on farms/haul big items...so I evolved it further by upgrading the wheels & tyres, cassette, bars, shifters, levers, and adding the X freeRadical classic cargo kit and purchasing things like a small solar charger for charging my phone and iPod, MSR gravity water filter bag and dromedary bladder, camp cooking items, and dry bags to carry my stuff in...even adding luxuries like the bottle cage speaker for listening to music on the rides:
In May I completed a 300mi. journey from FL> northern MS with my GT-X loaded with all my stuff. Im guessin the gear I had on my bike was b/w 50-70lbs. I had to bring things like hiking boots and long pants and my 15" laptop for a job surveying forest songbirds and working on an organic farm.
Now I'm dropping some of this extra weight in clothes and boots in preparation to ride out to CO next week and next year hopefully out to the west coast. So far, this has been an excellent bike to me for the almost 12years I've owned it. It's evolved beautifully with my evolving needs over the years as a carfree lifestylist.
If you want to plunk down almost 2 grand for the Bigdummy complete, you will not be sorry. You will get many long years of use out of the bike for sure! But consider retrofitting an older mtb or roadbike with the classic cargo kit for just as much fun and use at a much cheaper price! I hiiiiiiighly recommend the Xtracycle classic cargo kit (completely bolt-on: the kit comes with extra chain, new cables and housing, kickstand, and all the nuts &bolts you need). As far as the weight over the rear, it performs like it should. The free rad is rated for 250lb. max over/in front of the rear axle...and I hope you're not planning on taking that much gear on tour with you. I like it better than using trailers, as I feel like trailers "pull" back alot (esp. if the trailer hitch has a spring component).
Xtracycles are also perfect for barhopping with a friend or date on the back