Whilst I'm confident it would hold Buzz, I would feel the same as you and not 'trust' it. Trust is important considering what will be on it. The middle shelves have the benefit of uprights supporting them and will likely be strong (if you roll a sheet of paper into a tube you'll be amazed the weight it can support) but I'm concerned that the shelves which meet the side walls will only be attached by pegs or screws. Being chip board, over time they may crack through especially if you're planning to take the boxes on and off regularly.
For peace of mind, I would look for a strong metal equivalent. We had them in our work office and you can put an elephant on them. There's nothing worse than wondering if something is going to collapse, even if it is never going to.