Last summer I took Physics 1 during summer session 1. Then I took Orgo 2 in the morning and physics 2 at night during summer session 2. Thats a total of 13 credits this past summer. I made it out with all three As.
Doable? yes. difficult? scale of 1-10 i'd say about a 8.97253
Ahh, this is what keeps my hopes up about taking ochem 1/2 over the next summer.
Something I've noticed time and time again about "hard/difficult" courses/programs, more often than not the people who have had more trouble speak out the most, where as the people who kicked ass are often quiet. And I also note that whenever I've encountered this attitude of something being insanely hard, it's never even close to that degree when I have to do it.
Another thing I like to keep in mind, is that when you compare a summer course vs the same over a semester, yeah the thing is condensed and intensive, but you also don't have 4 other classes to contend with, including probably another science course; so based on that logic alone they should be comparable.
Finally, if this was the first time I'd ever taken classes (say I was a Freshman, or 18 or something), then I might be concerned about "retention" of information, especially for the DAT; however because I've had plenty of experience, experiencing how I retain information, I know that taking gen chem over the year (2 regular semesters) didn't make me remember anything particularly well, despite studying hard and doing very well. I think retention is really about the individual student.