I use 24% CP on a DM basis in my ration balancer for corn gluten feed. The majority of dry CGF comes pelleted (average pellet quality; plenty of fines). The benefits are that it is an economical protein source that is low in starch and high in fiber (less bloat, founder), and is high in phosphorus. Things to watch with CGF are high sulfur content, which TJ already mentioned, it can be toxic and can cause sulfur induced polio (treatable with injectable Thiamin). Also, it does have some palatability issues, so you do have to start cattle on them slowly. As a nutritionist my thumb rule for feeding CGF is to limit it to 0.5% of body weight. Example: 600# calf can be safely fed up to 3# of CGF per day. My best results with CGF have been when it is mixed with corn or soyhulls or something else to dilute the sulfur. Also, if you feed the higher levels of CGF, you won't need much phos in your ration, so pick a high calcium, low phos mineral, which will also save you a few bucks.
If you are asking about wet gluten, corn gluten meal, wet or dry distillers, these feeds are all different and have different benefits and challenges.