Agree with Street on water. If for some reason you don't want your BBQ to get hotter than 100C then it's good at keeping temp low, but all the heat goes in to steaming the water otherwise.
I had a go at the pork tinga the other week after seeing some great results on here, I tried to not worry too much about checking the temp in the pork and just gave it a good 2 hours at 250F, followed by 2 more hours with the pork in the sauce. Issue I had was, I haven't got a proper dutch oven. We have le creuset dishes but those are off limits for going in the BBQ, so the best thing I had was the enamel insert from our slow cooker. I was too chicken to put it over direct heat though, as he does in the video recipe, which I guess is key. So I tried to give it a bit longer but I had to finish her off in the oven (classic :[) to get the pork tender enough.
One thing I want to ask to guys with the dutch ovens, I read that you shouldn't simmer stuff in them for a long time because acidic sauces will break down the metal you get a metallic taste coming into the sauce. I have a cast iron pan but I try and look after it well and although I know it would obviously put up with the direct heat from my smoker, there is no way I'll simmer a tomato based sauce in it!
The pork was seriously tasty, though my sauce was a little watery, I think due to not having high enough heat for the duration. Definitely worth doing though, few things please me more than my toddler clearing his plate of bbq and it saved cooking for about 4 more meals that week.
Whacked a leg of lamb on for Easter Sunday too, smothered in garlic and rosemary. I left it until 140F internal, which I thought would be the right temperature but it definitely wanted a little more. The edges were beautiful, really juicy with a gentle smokey flavour, but closer to the bone was definitely a bit under so I put it back on for another 30 mins. The fat doesn't look very rendered below but it was moreso than it looks, and those reddish bits on the end, my word.
Did some pork belly slices just now, standard pork based rub and cooked for 2.5 hours, served with sweet potatoes also done on the smoker and sugar snaps peas. No pictures, ate it too fast. The pork was good but another 45 mins would have been perfect, the sweet potato was magic though, little oil and salt and it was fantastic. They were on the smoker for about an hour and ten I think, they weren't huge so it was long enough for them to be properly soft through, seriously nice.