I'm in second year biomed right now and so far I've found undergrad to be very demanding and stressful, especially second year, since they stacked all the difficult courses all in one year. I think the most stressful part of the whole thing is the fact that you need to consistently (almost without fail) score 90s on all your midterms and finals to get the 4.0s. Sometimes this pressure can be immense. Looking at my friends in engineering, where the material is definitely harder, non of them seem to be too burdened, which I think is due to the fact that they don't need to consistently score at the top of their class.
So far I haven't found undergrad to be enjoyable due to consistent pressure and uncertain future of doing a science degree. I don't hate it, but I don't find it enjoyable by any means. I found that actually getting high grades and seeing the results is one of the major things that motivates me to push through