The reviews are correct, I had one of those shelf units once and the MDF warping under load is exactly what it did.
I've been using NSF chrome wire shelving for years now. It's about $80 to $100 for a 4 or 6 shelf 2-foot by 5-foot unit depending where you buy it. The shelves are rated for 600lbs or 800lbs depending on the unit and they don't bend or warp.
IIRC, you can get it at costco and sam's club or any food service supplier.
This stuff:
