DK...
As a relatively new UDS owner (we have made about 8 in the last 3 months) I have to tell you that in our experience we have to keep one, two or all 3 holes open sometimes! Most of the time 1 will do the trick and if you regulate it with a ball valve it's a great start.
Now, if it's windy, cold, raining, your charcoal is burning down, etc...you may find you need 2 or even all ports open to get the temp where it belongs.
As far as the temp goes, we cook between 200 and 230 for most of our food. It's fairly easy to maintain those temps with the UDS. Even easier with a 16 quart stainless steel drip/water pan ($8). This also prevents a majority of the flare ups you will undoubtedly encounter without it when you take the lid off to mop, check temps, move, or foil your goodies...It's even easier to maintain the temp with a stoker but that's another story and whole lot more than the $8 water pan.
Hope this helps.
