Did someone already say both??
I have a mini and a full size and I use both of them!
You already know all the great stuff about the reg UDS, so here's what I love about the mini...
If you're headed out camping (or tailgating), you'll prolly take a grill anyways - the smokey joe is the perfect size for that! What's that?? You'd like to toss a butt on while you're off foraging for roots & berries in the forest? Good thing you did the mUDS mod to that SJ!
I think the consensus is that you'll get about 5+ hours of burn with out any sort of charcoal basket in the bottom (just use the lower charcoal grate as if you were grilling) and 6+ hours if you have a basket for it. I used a 6" wide strip of expanded metal (not SS) and formed it into a circle, no bolts or welding and it stays in it's shape just fine. Just set it on the charcoal grate.
I have the SJ silver (vents on the sides) and was really worried that it would either get way too much air (vents don't close very tight) to keep the temps down in the 250 range or that it wouldn't get enough air since the vents are above the charcoal grate level.
Wasn't even an issue - the sucker cranks along at 250 rock solid with the vents barely cracked and I can also close them completely and put the fire out if I want to.
Adding fuel is really easy, just lift the upper barrel portion off the kettle base and dump fuel in and replace the barrel, takes less than 30 seconds.
The draw backs - yeah it's small, you won't be cooking for a crowd with this thing, but that's not what it's meant for anyways...
Burn time, not going to get the long burns that the full size does, but IMO - 5 to 6+ hours is pretty dang good for a small fella like that and adding fuel is so easy, who cares right?
Let us know how the build goes!