First and foremost, I have been quite happy with my experience on DDB as a whole as a DM. I am actually in the process of writing a review/article on my experiences so far. However, tonight my group started the prep for a new campaign that is giving one of the players a chance to DM. One of the biggest hurdles was in homebrew options. His campaign has somewhat of a Valerian, city of a thousand planets vibe to it, and he was open to us using any homebrew race with approval. Two of the players ended up going with homebrew races, and quickly realized that meant they would not be able to use DDB for our newest campaign at all. I, and another player, chose Goliath races, so we were at least able to build our characters. We stuck to classes from the books, which meant us two Goliaths were able to build our characters about 95% of the way. The hurdle for the two of us came with awarded feats. We were all given feats based on our backgrounds, but there is nowhere to add a feat if you're not at a level where you'd get one normally. I imagine this is a problem for other DMs as well, since I know some people like to give out feats as quest rewards or at key points in the story. A few other gripes that I've had while playing with DDB so far. In one of the campaigns I am running, I opened up the UA for players, with the understanding I would make tweaks if necessary. Much like with the homebrew races, those players can just not use DDB at all for those characters. I know that Xanthars is just a little bit around the corner, and I pre-ordered the physical book day 1, but in the mean time, the inability to add UA stuff is also hurting us as a group. A final one that I just found last night and it bugged me more than it probably should have, is starting equipment. So much of DDB is set up with interactive webforms, yet when you go to add equipment for a new character, it completely drops the ball. The starting equipment is hidden behind a More menu, but even clicking on it doesn't really help you. You're given a plain text list like in the books themselves for starting equipment. This means you have to click back and forth multiple times to add your starting equipment. A much better way would be drop downs. Each section, pick A or B. If one has sub options, then add another drop down to satisfy those. Just a bit of personal feedback now that I've gotten the chance to actually set up a full new campaign on DDB.

This 1000%. 99% of my campaigns take place in Eberron, and so players being able to choose from UA: Eberron is out of the question if they want to use DDB to easily make a sheet. I find the lack of ability to add these custom things a bummer. I think, at the very least, the DM of the campaign should be allowed to edit in these races and feats on the character sheets submitted to them.