I feed beet pulp in addition to alfalfa chaff, coarse mix and bran, and I find it fab for keeping condition and maintaining a high fibre diet with greater calorie intake. It is high in calcium, so you have to balance it properly, especially with young stock, but that's the same with any feed... Feed oats on their own and you have too high starch and phosphorus, for example. You have to balance the ration, and as a high fibre, high calcium, high calorie feed you have to use it when it is required.
I've always found my horses love it, but I only feed a measuring cups worth before soaking in a large feed, so it's far from the only ingredient. I also always feed unmolassed!