I agree with the previous two posts. I was attending an IB school my first year, but then transferred to my neighborhood high school for my second year. I am a STEM student who was accelerated in math (Calc BC as a freshman), and found the IB Math HL curriculum (covering precalculus and calculus up to BC) to not be nearly challenging enough for my sophomore and junior years when I would be pursuing the diploma. The science curriculum as well wasn’t that strong (most SL), but that was likely a school specific issue. I ended taking three years of math at community college (and later at a state university), along with above-Physics C physics courses and some CS and Bio as well. I think this, rigor-wise, would likely have been more impressive than taking Math HL as part of the diploma. Even if it makes no difference with respect to college admissions, when I talk with my peers who were freshmen as well in my AP Calc class, I will have 40-50 more college credits than they will purely because I took a mix of community college and AP courses versus the IBDP.
For non-STEM students, thought, the IBDP seems awesome.