The structure is stable and easy to set up. We have two of them in our home office. While very simple design they are more than sturdy enough. Quality of the desk surfaces isn't the greatest but acceptable for us. The only issue for us has been the cross rails in back are too low to slide our larger tower PC under the desk so I drilled new holes and mounted one higher to accommodate.
This is my 3rd Gillespie Desk. I bought the first one about 5 years ago and it is still going strong. They are being used in my home office and in my son’s home schooling room. First of all yes the tops are thin and made of particleboard. I would not put a ton of weight on them but they are more than adequate for writing and a desktop computer setup. As long as you use your head about their limits they perform great and at a great price.