I just finished up my most recent batch of beer! It was a 3 gallon extract batch of gluten free blackberry ale. It has a nice balanced flavor with a tart finish. If you are looking to brew an extract batch of homemade gluten free beer, I highly recommend it.
Dextrins, and in this case specifically maltodextrins, are a group of mostly unfermentable carbohydrates produced by the partial hydrolysis of starch or glycogen. Dextrins and maltodextrins typically impart little to no flavor upon the finished beer, but are important because they can be a valuable method for adding gravity and perceived body and mouthfeel to a beer. This can be extremely helpful when you are brewing a heavy adjunct based beer such as a gluten free ale that might have a thin body. Maltodextrin is often made from corn, and a typical composition will be .5% dextrose, 2.5% Maltose, 3.5% maltoriose, 93.5% higher saccharides. You will want to consult your vendor for actual numbers.