Like any publisher, DDP can be slow at times and very quick at other times in communicating.
DDP does its own editing but the author is expected to participate in that the author may be asked to rewrite some sections or will be asked to approve of changes.
Likewise, DDP provides its own cover art. Much of the time the artwork is good. Occasionally, it lacks in some aspects such as showing grit on chains in a desert scene or dust on boots. I figure that's just artistic license since other artwork goes to the extreme in showing detail.
Ebooks do not have a strong market yet, but they're improving gradually. DDP seems to do well with those. I have a number of ebooks with DDP and can attest that you'll probably do better with a large print publisher, but DDP is honest and their checks generally arrive on time. Keep in mind that they're in Canada. That does affect what I call being on time since I'm in the US.
Their publishing schedule is not as good as I'd like to see. At times it seems like they've got too much on their plate. For example, I recently had two manuscripts go through editing, but only one has been released even though the editing took place back in January.