Mornin', Smitty, and welcome. Tons of info here that you can filter through on nearly any smoking topic. I looked through the link provided above, but I didn't see much about the 3 in 1: you may want to also try "Oklahoma Joe triple burner" in the search engine and there are a few other posts you'll find.
My thoughts on this unit. You're certainly gaining convenience and footprint by using something like this. Won't have to have 2 dedicated units for gas grilling and charcoal smoking, thus more convenient and less space occupied. But, as with everything else with multi-purpose tools, you're likely sacrificing quality and functionality on each for convenience sake--think of a Swiss army knife vs. each dedicated tool found within. Think also if one aspect of this goes bad (whether it's the gas side or the smoke side), you may have lost the functionality for the entire unit. My advice would be to think about what you're going (or want) to be cooking the most, and how you're going to do it. Then formulate a decision from there as to what type of rig would be best for what you're trying to accomplish. Then start honing in on different brands to make an educated buying decision. If you're simply looking at this as a "one size fits all" type of approach and that it's the cheapest option for you right now, don't do it. Buy quality, buy once--will likely cost you less in the long run. My $0.02