It is absolutely NOT a sin to use a meat thermometer. Knowing the internal temperature of the meat is very important for many reasons. Spend some time on this forum and you'll see that most of us rely on accurate temperature readings for many things, food safety the most important among them.
In grilling, accurate internal temperature readings are the best way to ensure proper doneness. That applies especially for poultry, where things can go from unsafely under cooked to over cooked very quickly. Even on the bigger cuts in BBQ, knowing the internal temperature is important. For those who wrap their meats in foil (I'm one of them), it's usually done at a particular internal temperature. Pork shoulder can sit for hours at 165 degrees IT or so, so I wrap as soon as it reaches that temperature to push it through the stall. When it reaches 185, it's ready to slice. 195 to 200 and it's ready to pull.
Brisket on the other hand is not so predictable, but you'll still want to know the internal temperature. It might be done anywhere from 180 (rarely) or 190 (a little more often) or 200 (most often) or above. You'll have to probe the meat to feel for doneness, but it's a good idea to know when to start and understand what's going on inside the meat.
All that said, the Maverick ET-732 remote thermometer is one of the best on the market these days. You can buy it from one of several Brethren's online stores, check out Brethren Sales and Ventures. For instant read thermometer, you can't go wrong with a Superfast Waterproof Thermapen.
Good luck and Smoke On!
