I have worked at a university with students who transfer from early college programs, and there are several issues I have seen. One is that they come into the university with 60+ hours of credit, so they are instantly thrown into junior level classes, but they are still 18 and may not have the maturity or a rigorous enough background at the community college to do well. Of course there are exceptions, but quite a few of them end up in academic trouble. They often come into the university with the expectation that they will easily finish in two years, but that is almost never the case. With some majors it can work, but many of these students want to do STEM, and it just doesn't work well for those majors because of prereq issues and lack of preparation for the rigor of university-level science and math courses. It also seems like the early college schools are really insular and students are in a small cohort together for several years which I think is probably not good for their social development (but in our state, early college programs vary widely, so this may not always be true). In short, many of them seem to struggle socially and academically when they get to university. It's so different from CC/EC, and it just seems to be a tough transition for them.
I think the sweet spot is to get up to 30 hours of dual enrollment credit, which, if planned well, could knock off a semester or two of time to degree but doesn't put a student so out of sync with other university students (in terms of age and credits earned) that they feel they are a fish out of water. What I really wish more students would do is take a gap year and grow up, have some experiences, gain a little insight into who they are and what they want to do. I don't understand the rush to get through college (except for concerns about cost; I get that, but in the long run, most students need at least 3 years to finish, so it doesn't save that much $$ anyway). It can work for students who are really focused and academically strong, but it's not a good route for every student in my opinion.