Just as a note - the original poster said the summer semester in question would be a full, 4-month semester. Almost every post since then has dealt at least in part with the speed of summer classes, and shortened time, and resultant difficulties in keeping up or properly absorbing everything, which are kind of moot given the length of their summer semester 😀
As NJB mentioned, there shouldn't be any stigma whatsoever associated with summer classes. The exception, as mentioned by another poster, would be if you were taking the summer classes at a "lower-level" institution than you normally attend. Since you mentioned taking one semester in the winter/spring and one in the summer, it doesn't sound like that's the case.
I took Organic I and Cell Bio over this past summer. The school I'm at offers a 13 week summer semester (as compared to a 16 week normal semester). I thought the summer classes were great because they were a lot easier for me to get into than fall/spring semester classes, and also because with a lot less students on campus everything just feels more relaxed. The classes were just as demanding, but students felt a bit more laid back, and professors were more accessible outside of class because of a dearth of other students needing their help/time. I never had to worry about waiting in line for a PC at the computer lab, or lack of space in the cafeteria or lounge, or anything else along those lines that can be problems during the fall/spring when school is packed with students.
If at all possible I'd like to get involved in some research next summer, but if that isn't the case I would gladly take summer classes again. Heck, I wish all my classes were summer classes after really thinking about how different things felt than the regular schoolyear.