Don't know much about Osburn but I can tell you a little about my experience with our Quadra-fire voyager grand insert. We have had it for four seasons now.
It burns very clean, most of the time you don't even see smoke coming out of the chimney. We went two seasons before cleaning the chimney and only got a few handfuls of soot (maybe 2 cups) when we finally did clean it.
The Automatic Combustion Control - this feature is nothing more than an air inlet that slowly shuts down the air coming in on a timer. When you add a log you push in the control knob and the timer starts, it allows a lot of air at first to get the log going and then slowly shuts it down. I like this feature for when we leave the house for a while, I can throw a few logs in and set the timer and walk out knowing that its not going to be burning at full throttle the whole time, or just smoldering because I added too much wood and not enough air.
Very picky about the wood you use. Must use dry wood, anything green will just smolder, soot up your glass and your chimney. Our first season was rough because we did not have much cured wood. The stove is so tight that it just wouldn't burn, I had to leave the door cracked open just to get enough air in to burn the green wood. If you don't have dry, cured wood, the two items I mentioned under "the good" are null and void. To be fair, I believe that this is an issue with all of the modern stoves that have secondary combustion features and is not limited to the quadra-fire brand.
The Automatic Combustion Control - Yes it has a down side. Its intended to be extremely user friendly and it is. The draw back is that sometimes I just want more control in order to fine tune it and I can't when that timer is going. Once its set, its set, and it has to run its course (about 20 min). I have learned to adapt, read the fire and the wood I'm putting in and make a judgement call on using it or not.
Overall we are very satisfied with it. In general you get what you pay for and I'm sure the Osburn is fine stove as well.