I have a New Braunfels cooker with an offset firebox that I love dearly. Apparently New Braunfels has now been swallowed by Charbroil. Ah, well.
However, it is the design I love, no matter who makes it. It is wonderful to be able to cook ribs and chicken, (and other meats that tend to turn into torches as soon as you turn your back on a standard grill) with nary a care in the world. If you entertain, it allows you to go mingle with your guests instead of constantly hovering over the grill with a spray bottle.
Two accessories I would recommend. First, (if the company your cooker is made by offers it) splurge, and get the propane starter. With one of these cookers, it is definitely worth it to use genuine charcoal, rather than briquettes, and this can be a little harder to start. Yes, you can use a chimney starter, (and probably will if you need to refill your firebox while cooking) but it is just so danged easy and quick to pour your charcoal in, fire up the propane burner, and get cooking in a matter of minutes. (The propane burner is only to start your charcoal and quickly get it to the coals stage and ready for cooking. You don't actually use the propane for cooking your meat.)
Second, get one of those remote probe thermometers. You know, the wireless kind that has a probe connected to a transmitter, and a receiver you can take with you and check the temperature of your meat from virtually anywhere on the premises. I have one made by NU-Temp that I have had for years and still works just dandy, but I am sure by now there are many to choose from. Just make sure it has an audible alarm to tell you when your meat is done. Recently I saw one that had dual probes and readouts; one to tell you the temperature of your meat, and another to tell you the temperature inside your cooker. This would be THE one to have. This way, not only could you monitor the temperature of your meat, you could tell if your firebox needs refilling.
At one party I was having recently, a couple had eaten my ribs, then accosted me to demand my "recipe for the marinade." All I had done was to dust the ribs down with seasoning salt and garlic powder, and cooked them with mesquite charcoal. That was a good feeling.
Oh, and one other thing. When I first cooked ribs, (and before I got the thermometer) I kept checking them to see if they were done, and couldn't understand why they were still red after quite a long time of cooking. Well, that was the "Smoke ring" which is a very desirable thing with this kind of cooking. Ideally, a caramelized crust will form with the smoke ring underneath, but if you don't cook it quite hot enough, all you will see is the red smoke ring. It's about the color of the red edges on the barbequed pork at a Chinese restaurant. If this happens to you, check with a thermometer.
A nice thing about this kind of cooker is you have an amazingly large window as to when ribs are "done", so my first rib effort came out just fine, even though I did cook them for way longer than necessary.