Tried it again last night hooked to my new UDS and it worked flawlessly. I was able to set temp and watch it bring the cooker up to temp then maintain. I did notice that removing the lid does case the things to swing as it tries to get temp back on track. I found that if you turn the unit off just before removing the lid it'll adjust much faster once the lid is back in place.
I'm liking this Golden Dog/QMaster Junior enough so that I'm planning on picking their new QMaster Senior which is a two probe unit to monitor and regulate cooker temp and food temp. Hard to beat for the $150 their asking!